U.S. patent application number 16/465309 was filed with the patent office on 2019-12-26 for light-emitting device and image display apparatus including the same.
This patent application is currently assigned to DIC Corporation. The applicant listed for this patent is DIC Corporation. Invention is credited to Yoshio Aoki, Shinji Ogawa, Yasuo Umezu, Hidehiko Yamaguchi.
Application Number | 20190393273 16/465309 |
Document ID | / |
Family ID | 62711090 |
Filed Date | 2019-12-26 |
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United States Patent
Application |
20190393273 |
Kind Code |
A1 |
Umezu; Yasuo ; et
al. |
December 26, 2019 |
LIGHT-EMITTING DEVICE AND IMAGE DISPLAY APPARATUS INCLUDING THE
SAME
Abstract
It is an object of the present invention to provide an image
display apparatus capable of inhibiting or preventing the
deterioration of a light conversion layer while high luminous
efficiency and high color reproducibility are achieved. The present
invention provides a light-emitting device including a pair of
electrodes, an electroluminescent layer disposed between a first
electrode and a second electrode, a light conversion layer
including multiple pixels and converting light that is emitted from
the electroluminescent layer and that has a blue emission spectrum
into light having a different wavelength. The light conversion
layer includes pixels of three primary colors of red (R), green
(G), and blue (B) and contains a light-emitting nanocrystal having
an emission spectrum in any of red (R), green (G), and blue (B)
when light from the electroluminescent layer is incident on at
least one of the three primary colors.
Inventors: |
Umezu; Yasuo;
(Kitaadachi-gun, JP) ; Yamaguchi; Hidehiko;
(Kitaadachi-gun, JP) ; Aoki; Yoshio;
(Kitaadachi-gun, JP) ; Ogawa; Shinji;
(Kitaadachi-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DIC Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
DIC Corporation
Tokyo
JP
|
Family ID: |
62711090 |
Appl. No.: |
16/465309 |
Filed: |
December 21, 2017 |
PCT Filed: |
December 21, 2017 |
PCT NO: |
PCT/JP2017/045920 |
371 Date: |
May 30, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/3211 20130101;
G02B 5/206 20130101; H01L 27/322 20130101; H05B 33/12 20130101;
H05B 33/14 20130101; C09K 11/70 20130101; H01L 51/5221 20130101;
H01L 51/5284 20130101; G02B 5/201 20130101; H01L 51/5012 20130101;
H01L 51/5036 20130101; C09K 11/06 20130101; C09K 11/54 20130101;
C09K 11/56 20130101; H01L 51/5206 20130101; G02B 1/14 20150115;
G02B 5/20 20130101; H01L 27/32 20130101; H05B 33/02 20130101; H01L
2251/5369 20130101; H01L 51/50 20130101; H01L 2251/5376 20130101;
G09F 9/30 20130101 |
International
Class: |
H01L 27/32 20060101
H01L027/32; H01L 51/50 20060101 H01L051/50; H01L 51/52 20060101
H01L051/52 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2016 |
JP |
2016-255101 |
Claims
1. A light-emitting device, comprising: a pair of electrodes
including a first electrode and a second electrode disposed
opposite each other; an electroluminescent layer disposed between
the first electrode and the second electrode; and a light
conversion layer including multiple pixels and converting light
that is emitted from the electroluminescent layer and that has a
blue emission spectrum into light having a different wavelength,
wherein the light conversion layer includes pixels of three primary
colors of red (R), green (G), and blue (B) and contains a
light-emitting nanocrystal having an emission spectrum in any of
red (R), green (G), and blue (B) when light from the
electroluminescent layer is incident on at least one of the three
primary colors.
2. The light-emitting device according to claim 1, wherein the
electroluminescent layer contains one or two or more light-emitting
materials selected from the group consisting of an inorganic
light-emitting material, a low-molecular-weight fluorescent
material, an organic polymer fluorescent material, a phosphorescent
material, and a thermally activated delayed fluorescent
material.
3. The light-emitting device according to claim 2, wherein the
low-molecular-weight fluorescent material is a compound having at
least one selected from the group consisting of an anthracene
moiety, a tetracene moiety, a chrysene moiety, a phenanthrene
moiety, a pyrene moiety, a perylene moiety, a stilbene moiety, an
acridone moiety, a coumarin moiety, a phenoxazine moiety, and a
phenothiazine moiety.
4. The light-emitting device according to claim 2, wherein the
phosphorescent material is a metal complex containing at least one
metal atom selected from the group consisting of iridium, rhodium,
platinum, ruthenium, osmium, scandium, yttrium, gadolinium,
palladium, silver, gold, and aluminum.
5. The light-emitting device according to claim 2, wherein the
light-emitting material contains one or two or more host materials
each having a larger energy gap than the light-emitting
material.
6. The light-emitting device according to claim 2, wherein the
light that is emitted from the electroluminescent layer and that
has the blue emission spectrum has a peak at 420 nm to 480 nm.
7. The light-emitting device according to claim 1, wherein in the
light conversion layer, an emission spectrum of at least one of red
(R), green (G), and blue (B) has a full width at half maximum of 20
to 50 nm.
8. The light-emitting device according to claim 1, wherein in the
light conversion layer, the light-emitting nanocrystal includes a
core containing at least one or two or more first semiconductor
materials, and a shell covering the core and containing a second
semiconductor material identical to or different from that of the
core.
9. The light-emitting device according to claim 7, wherein the
first semiconductor material is one or two or more selected from
the group consisting of II-VI group semiconductors, III-V group
semiconductors, I-III-VI group semiconductors, group IV
semiconductors, and I-II-IV-VI group semiconductors.
10. An image display apparatus characterized by having a light
emitting device according to claim 1, comprising a transistor layer
electrically connected to the first electrode or the second
electrode, wherein the light emitted from the electroluminescent
layer is displayed through the light conversion layer and the
transistor layer.
11. An image display apparatus characterized by having a light
emitting device according to claim 1, comprising a transistor layer
electrically connected to the first electrode or the second
electrode, wherein the light emitted from the electroluminescent
layer is displayed without passing through the transistor layer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a light-emitting device and
an image display apparatus including the light-emitting device.
BACKGROUND ART
[0002] In recent years, flat-panel displays (FPDs) having thin flat
screens have been in the mainstream of display devices in place of
cathode-ray tubes (CRTs). Examples of FPDs include liquid crystal
displays, organic electroluminescent (organic EL) displays, plasma
displays, and field emission displays (FEDs). Recently, the
developments of organic EL displays and liquid crystal displays
have been particularly actively conducted. The development of
mobile computing increases demands for display devices for portable
information terminals and requires reductions in weight and power
consumption of display devices and the development of a foldable
display device. For these reasons, self-luminous organic EL devices
have been receiving attention.
[0003] EL devices such as organic EL devices are self-luminous, do
not require a back-light, can be made thin and lightweight, have a
few members, and can be easily made foldable. However, El devices
have problems such as display defects due to deterioration of
light-emitting members. Specifically, it is necessary to solve
problems such as high cost due to poor yield during the production
of devices, image-sticking of devices due to their lifetimes, and
display unevenness. Additionally, in the case of a full-color
organic EL device, red, green, and blue need to be independently
emitted. In particular, the foregoing problems are likely to occur
in blue, which is a high energy ray with a short wavelength. There
is also a problem such as the yellowing of devices due to the
fading of blue in long-term use.
[0004] To absorb the difference in the rate of deterioration among
members that emit three primary colors of light, various methods
have been examined. For example, disclosed is a method for
increasing the size of blue pixels using the fact that the human
eye has few blue receptors and low sensitivity, instead of reducing
the number of blue pixels with respect to the number of other
pixels (see Patent Literature 1). In this method, although the blue
pixels can be relatively large in size and the lifetime of the blue
pixels can be equivalent to those of other pixels, there is a
problem that the display quality has to be sacrificed.
[0005] As a method for eliminating the difference in
characteristics among pixels, a structure is disclosed in which
color filters of the primary colors (red, green, and blue) are
arranged on an organic EL device that emits white light (see Patent
Literature 2). This method has the following advantages: the use of
the pixels composed of the same material eliminates differences in
characteristics among the pixels and enables all pixels to have the
same size. To obtain white light, typically, a method in which a
blue LED and a yellow phosphor are combined together is often
employed and advantageously has good efficiency. However, the white
light source disadvantageously has insufficient characteristics
such as lack of red light. In the case of using the color filters,
an improvement in color reproducibility decreases the transmittance
of the color filters. The amount of light must be increased, thus
disadvantageously increasing the power consumption. It is
disadvantageously difficult to achieve differentiation from liquid
crystal devices.
[0006] As a method for achieving full-color display without using a
color filter, a method is disclosed in which blue light or
ultraviolet light from a light-emitting layer is used as a primary
light source and a wavelength conversion layer composed of, for
example, phosphor materials is irradiated with light emitted from
the light source to produce three primary colors as a secondary
light source (see Patent Literature 3). In this method, because the
light source may emit a single color, there is no difference in
characteristics among three primary colors, and there are only a
few problems such as a decrease in transmittance due to a color
filter. Furthermore, a technique in which quantum dots are used in
a wavelength conversion layer has been receiving attention. Quantum
dots are formed of semiconductor microcrystals having a particle
size of several nanometers to several tens of nanometers and have
discrete energy levels due to the confinement effect of
electron-hole pairs and a property that a smaller particle size
results in a larger energy band gap. A wavelength conversion layer
having a narrow full width at half maximum of an emission spectrum
can be obtained by the use of the property, i.e., by controlling
the particle diameter to equalize the band gap (see Patent
Literature 4).
CITATION LIST
Patent Literature
[0007] PTL 1: Japanese Unexamined Patent Application Publication
No. 2011-209754
[0008] PTL 2: Japanese Unexamined Patent Application Publication
No. 10-12383
[0009] PTL 3: Japanese Unexamined Patent Application Publication
No. 2015-125994
[0010] PTL 4: Japanese Unexamined Patent Application Publication
No. 2013-137931
SUMMARY OF INVENTION
Technical Problem
[0011] Regarding the characteristics of a phosphor material having
quantum dots used as a material of the wavelength conversion layer
and a light-emitting layer serving as a primary light source, there
are problems that the optimization of the characteristics thereof
is indispensable for the achievement of an optimum color gamut and
that the material therefor is difficult to select. If
light-emitting nanocrystals such as quantum dots and a
light-emitting layer are insufficiently optimized, a wavelength
conversion layer cannot sufficiently absorb light from the
light-emitting layer serving as a primary light source. Thus, light
that cannot be absorbed by the wavelength conversion layer is
transmitted therethrough. Light converted by the wavelength
conversion layer and light from the primary light source, which is
the light-emitting layer, are mixed together to cause a problem of
the decrease of the color reproducibility or a problem of coloring
due to the degradation of the wavelength conversion layer.
[0012] From the above reasons, in the display device having a
structure in which blue light or ultraviolet light emitted from a
light-emitting layer is used as a primary light source and a
wavelength conversion layer composed of, for example, a phosphor
material is irradiated with light emitted from the light source to
produce three primary colors as a secondary light source, the
optimization of the primary light source and the wavelength
conversion layer is required.
[0013] It is an object of the present invention to provide a
light-emitting device capable of inhibiting or preventing the
deterioration of a light conversion layer while high luminous
efficiency and high color reproducibility are achieved, and an
image display apparatus including the light-emitting device.
[0014] It is another object of the present invention to provide a
light-emitting device capable of inhibiting or preventing the color
mixing of light from a light-emitting layer and light that has
passed through a light conversion layer, and an image display
apparatus including the light-emitting device.
Solution to Problem
[0015] The inventors have conducted intensive studies to solve the
foregoing problems and have found that the problems can be solved
by the use of a light-emitting device including a pair of
electrodes including a first electrode and a second electrode
disposed opposite each other, an electroluminescent layer disposed
between the first electrode and the second electrode, and a light
conversion layer including multiple pixels and converting light
that is emitted from the electroluminescent layer and that has a
blue emission spectrum into light having a different wavelength, in
which the light conversion layer includes pixels of three primary
colors of red (R), green (G), and blue (B) and contains a
light-emitting nanocrystal having an emission spectrum in any of
red (R), green (G), and blue (B) when light from the
electroluminescent layer is incident on at least one of the three
primary colors. The finding has led to the completion of the
present invention.
Advantageous Effects of Invention
[0016] The light-emitting device of the present invention has good
transmittance and maintains a color gamut for a long time.
[0017] The light-emitting device of the present invention can
inhibit or prevent the color mixing of light from a light-emitting
layer and light that has passed through the light conversion
layer.
[0018] The image display apparatus of the present invention is not
easily degraded by high-energy rays such as short-wavelength
visible light and ultraviolet light, and maintains a color gamut
for a long time.
[0019] The image display apparatus of the present invention can
inhibit or prevent the color mixing of light from the
light-emitting layer and light that has passed through the light
conversion layer.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a schematic cross-sectional view illustrating a
light-emitting device of the present invention.
[0021] FIG. 2 is an enlarged schematic view illustrating an example
of a light conversion layer according to the present invention.
[0022] FIG. 3 is an enlarged schematic view illustrating another
example of the light conversion layer according to the present
invention.
[0023] FIG. 4 is a schematic cross-sectional view illustrating a
light-emitting device according to another embodiment of the
present invention.
[0024] FIG. 5 is an enlarged schematic view illustrating another
example of the light conversion layer according to the present
invention.
[0025] FIG. 6 is a schematic cross-sectional view illustrating a
light-emitting device according to another embodiment of the
present invention.
[0026] FIG. 7 is a schematic cross-sectional view illustrating a
light-emitting device according to another embodiment of the
present invention.
[0027] FIG. 8 is a schematic circuit diagram illustrating a
transistor layer according to the present invention.
[0028] FIG. 9 is a schematic circuit diagram illustrating a
transistor layer according to the present invention.
[0029] FIG. 10 is a schematic cross-sectional view illustrating an
image display apparatus of the present invention.
DESCRIPTION OF EMBODIMENTS
[0030] A first aspect of the present invention is directed to
providing a light-emitting device including a pair of electrodes
including a first electrode and a second electrode disposed
opposite each other, an electroluminescent layer disposed between
the first electrode and the second electrode, and a light
conversion layer including multiple pixels and converting light
that is emitted from the electroluminescent layer and that has a
blue emission spectrum into light having a different wavelength, in
which the light conversion layer includes pixels of three primary
colors of red (R), green (G), and blue (B) and contains a
light-emitting nanocrystal having an emission spectrum in any of
red (R), green (G), and blue (B) when light from the
electroluminescent layer is incident on at least one of the three
primary colors.
[0031] The light-emitting device of the present invention has good
transmittance and maintains a color gamut for a long time.
[0032] The structure of the light-emitting device according to a
preferred embodiment of the present invention will be described
below with reference to FIGS. 1 to 7.
[0033] FIG. 1 is a schematic cross-sectional view illustrating a
light-emitting device 100 of the present invention. The
light-emitting device 100 of the present invention includes a first
electrode 2 and a second electrode 8 serving as a pair of opposite
electrodes, an electroluminescent layer 12 disposed between the
electrodes, and a light conversion layer 9 on the second electrode
8. The electroluminescent layer 12 according to the present
invention may include at least a light-emitting layer 5. The
electroluminescent layer 12 according to the present invention
preferably includes an electron transport layer 6, the
light-emitting layer 5, a hole transport layer 4, and a hole
injection layer 3. The electroluminescent layer 12 according to the
present invention preferably includes an electron injection layer
7, the electron transport layer 6, the light-emitting layer 5, the
hole transport layer 4, and the hole injection layer 3.
Additionally, an electron-blocking layer (not illustrated) may be
disposed between the light-emitting layer 5 and the hole transport
layer 4 in order to enhance the external quantum efficiency and
improve the light emission intensity. Similarly, a hole-blocking
layer (not illustrated) may be disposed between the light-emitting
layer 5 and the electron transport layer 6 in order to enhance the
external quantum efficiency and improve the light emission
intensity.
[0034] In the light-emitting device 100, the electroluminescent
layer 12 has a structure in which the hole injection layer 3 in
contact with the first electrode 2, the hole transport layer 4, the
light-emitting layer 5, and the electron transport layer 6 are
stacked in this order.
[0035] In an embodiment of the present invention, in the following
description, for convenience, the first electrode 2 serves as an
anode, and the second electrode 8 serves as a cathode. However, the
structure of the light-emitting device 100 is not limited thereto.
The first electrode 2 serving as a cathode and the second electrode
8 serving as an anode may be used, and the layers between these
electrodes may be stacked in reverse order. In other words, the
hole injection layer 3, the hole transport layer 4, the
electron-blocking layer disposed as needed, the light-emitting
layer 5, the hole-blocking layer disposed as needed, the electron
transport layer 6, and the electron injection layer 7 may be
stacked in this order from the second electrode 8 adjacent to the
anode.
[0036] The light conversion layer 9 according to the present
invention serves as what is called a color layer, includes pixels
of three primary colors of red (R), green (G), and blue (B), and
contains light-emitting nanocrystals. When at least one color pixel
among the three primary colors is irradiated with light that is
emitted from the electroluminescent layer 12 and that has a blue
emission spectrum, the light-emitting nanocrystals convert the
light into light having an emission spectrum in any of red (R),
green (G), and blue (B).
[0037] One of the features of the present invention is that the
light conversion layer 9 containing the light-emitting nanocrystals
NC is used as an alternative member to a color filter. Thus, the
light conversion layer 9 in the present invention includes the
pixels of three primary colors, namely, red (R), green (G), and
blue (B) and plays the same role as what is called a color
filter.
[0038] Specifically, the light conversion layer 9, for example,
includes a red (R) pixel portion (red color layer portion)
including light conversion pixel layers containing
red-light-emitting nanocrystals (NC-Red), a green (R) pixel portion
(green color layer portion) including light conversion pixel layers
containing green-light-emitting nanocrystals (NC-Green), and a blue
(R) pixel portion (blue color layer portion) including light
conversion pixel layers containing blue-light-emitting nanocrystals
(NC-Blue). FIG. 2 illustrates an example of the light conversion
layer 9 of a single-layer type.
[0039] FIG. 2 is an enlarged schematic view illustrating the light
conversion layer 9 according to the present invention. The light
conversion layer 9 includes red color layers R, green color layers
G, and blue color layers B. A red (R) pixel portion R (red color
layers R) is formed of light conversion pixel layers containing
red-light-emitting nanocrystals (NC-Red). A green (G) pixel portion
G (green color layers G) is formed of light conversion pixel layers
containing green-light-emitting nanocrystals (NC-Green). A blue (B)
pixel portion B (blue color layer B) is formed of (light conversion
pixel) layers containing blue-light-emission nanocrystals as needed
(or a transparent resin layer). Accordingly, the light conversion
layer 9 is formed of a single nanocrystal layer NCL containing the
red color layers R, the green color layers G, and the blue color
layers B. To prevent color mixing, a black matrix BM serving as a
light-shielding layer is disposed between the red color layers R,
the green color layers G, and the blue color layers B.
[0040] Specifically, in the case where light having a main peak at
or near 450 nm (light having a blue emission spectrum) is emitted
from the electroluminescent layer 12, the blue light can be used as
a blue color in the light conversion layer 9. Thus, in the case
where light emitted from the electroluminescent layer 12 serving as
a light source is blue light, the light conversion pixel layers
(NC-Blue) may be omitted among the light conversion pixel layers
for each color (NC-Red, NC-Green, and NC-Blue), and backlight may
be used as a blue color on an as-is basis. In this case, the color
layers that display the blue color may be formed of, for example,
colorant layers containing a transparent resin or a blue colorant
(i.e., a blue color filter). In FIGS. 1, 2, and so forth, because
the blue-light-emitting nanocrystals can be an optional component,
the blue-light-emission nanocrystals are indicated by a
dot-and-dash line.
[0041] Each of the red color layers R, the green color layers G,
and the blue color layers B may appropriately contain a colorant,
as needed. Additionally, the layer (NCL) containing the
light-emitting nanocrystals NC may contain colorants corresponding
to the colors.
[0042] In FIG. 1, a colorant layer containing a blue colorant
(i.e., "blue color filter") is preferably disposed on one surface
of part of the light conversion layer 9 between them in accordance
with the electroluminescent layer 12 used or the wavelength of
light emitted from the electroluminescent layer 12 because the
entry of unwanted light from the outside can be prevented to
inhibit a deterioration in image quality. FIG. 3 illustrates the
structure of the light conversion layer 9 including the blue color
filter according to a modified embodiment.
[0043] As a light conversion layer according to a preferred
embodiment, the nanocrystal layer NCL illustrated in FIG. 2 and a
colorant layer CFL (i.e., a color filter) containing a colorant are
stacked in FIG. 3. In the case where light (excitation light, for
example, blue light) from the electroluminescent layer cannot be
completely converted in the light conversion layer, it is necessary
to absorb the remaining excitation light without allowing the
remaining excitation light to pass through the light conversion
layer. Thus, the light conversion layer inhibits the remaining
excitation light (blue light) from being viewed from the outside by
stacking a layer (NC) containing light-emitting nanocrystals and
the colorant layer CFL containing a colorant (i.e., a color
filter). However, the colorant layer CFL containing a colorant
(i.e., a color filter) may be omitted, as needed. In FIG. 3, a
colorant layer containing a blue colorant is disposed as the color
filter layer CFL because light having a main emission peak in a
wavelength range of 420 nm to 480 nm is assumed to be used as a
light source (light emission from the electroluminescent layer).
However, the type of colorant layer is appropriately changed in
accordance with the type of light source used.
[0044] Thereby, the image display apparatus of the present
invention can inhibit or prevent the color mixing of light from the
electroluminescent layer and light that has passed through the
light conversion layer.
[0045] In the light-emitting device 100 illustrated in FIG. 1, the
application of a voltage between the first electrode 2 and the
second electrode 8 permits electrons to be injected from the second
electrode 8 serving as a cathode into the electroluminescent layer
12 and permits holes to be injected from the first electrode 2
serving as an anode into the electroluminescent layer 12, so that a
current flows. The electrons and the holes injected are recombined
to form excitons. As a result, the light-emitting material
contained in the light-emitting layer 5 is in an excited state to
emit light from the light-emitting material. Then light emitted
from the light-emitting layer 5 is incident on a surface of the
light conversion layer 9 through the electron transport layer 6,
the electron injection layer 7, and the second electrode. The light
incident on the light conversion layer 9 is absorbed by the
light-emitting nanocrystals and converted into light having an
emission spectrum in any of red (R), green (G), and blue (B), so
that any of red (R), green (G), and blue (B) can be displayed.
[0046] A preferred embodiment of the present invention provides a
light-emitting device that displays any of red (R), green (G), and
blue (B) by emitting blue light from the light-emitting layer 5,
allowing the blue light to be incident on the light conversion
layer 9, allowing the blue light to be absorbed by the
light-emitting nanocrystals, and converting the absorbed blue light
into light having an emission spectrum in any of red (R), green
(G), and blue (B).
[0047] Color display methods in organic light-emitting devices
(OLEDs) typically include (1) a display method in which
light-emitting materials that exhibit three colors of red, green,
and blue are separately formed into films; (2) a display method in
which three colors are displayed by a combination of a
light-emitting layer that emits blue light, a color conversion
layer that converting the blue light from the light-emitting light
into green light, and a color conversion layer that converting the
blue light from the light-emitting layer into red light; and (3) a
method in which a light-emitting layer that emits white light and
red, green, and blue color filters are combined together. In the
present invention, the display method (2) is preferred because
colors are displayed using the light-emitting nanocrystals.
[0048] In the electroluminescent layer 12 according to the present
invention, a single layer or multiple layers that provide various
effects may be disposed for the purpose of reducing a potential
barrier to injection of holes or electrons, improving the transport
characteristics of holes or electrons, impairing the transport
characteristics of holes or electrons, or inhibiting or preventing
a quenching phenomenon due to the electrodes, if necessary.
[0049] An overcoat layer 10 may be disposed as a protective film so
as to cover the light conversion layer 9. If necessary, a substrate
11 composed of, for example, glass may be bonded to the entire
surface of the overcoat layer 10. In this case, a known adhesive
(for example, a thermosetting or ultraviolet curable resin) may be
disposed between the overcoat layer 10 and the substrate 11, as
needed. As described below, in the case where the light-emitting
device according to the present invention is a top emission type in
which light emerges from the substrate 11, the overcoat layer 10
and the substrate 11 are preferably composed of a transparent
material. As illustrated in FIG. 10 below, in the case of a bottom
emission type in which light emerges from a substrate 11, the
overcoat layer 10 and the substrate 11 are not particularly
limited.
[0050] FIG. 1 illustrates a structure in which the first electrode
2 is disposed on the substrate 1. The substrate serves as a base
that supports a stack including the first electrode 2, the
electroluminescent layer 12, the second electrode 8, and the light
conversion layer 9. A known substrate may be used as the
substrate.
[0051] FIG. 4 is a schematic cross-sectional view illustrating the
light-emitting device 100 according to another embodiment of the
present invention. The structure according to the embodiment
illustrated in FIG. 4 has the same structure as in FIG. 1, except
for the light conversion layer 9; thus, the description is omitted
here. In red and green color layer portions included in the light
conversion layer 9 according to the embodiment illustrated in FIG.
4, the red color layer portion has a two-layer structure in which a
light conversion pixel layer (NC-Red) containing red-light-emitting
nanocrystals and a colorant layer (i.e., a red color filter)
(CF-Red) containing a red colorant are stacked, and the green color
layer portion has a two-layer structure in which a light conversion
pixel layer (NC-Green) containing green-light-emitting nanocrystals
that emit green light and a colorant layer (i.e., a green color
filter) (CF-Green) containing a green colorant are stacked.
[0052] Regarding the two-layer structures of each color layer, when
light emitted from the electroluminescent layer 12 cannot be
entirely converted by the light conversion pixel layer containing
the nanocrystals, a color filter (CFL) or a colorant layer for each
color is stacked for the purpose of absorbing remaining excitation
light without allowing the remaining excitation light to pass. More
specifically, the light conversion layer 9 includes the red color
layer portion, the green color layer portion, and a blue color
layer portion. The red (R) pixel portion (red color layer portion)
has the two-layer structure including the light conversion pixel
layer (NC-Red) containing the red-light-emitting nanocrystals and
the colorant layer (CF-Red) containing the red colorant. The green
(G) pixel portion (green color layer portion) has the two-layer
structure including the light conversion pixel layer (NC-Green)
containing the green-light-emitting nanocrystals and the colorant
layer (CF-Green) containing the green colorant. In this case, the
green color layer portion illustrated in FIG. 4 may also be a
combination of a light conversion pixel layer (NC-Green) containing
green-light-emitting nanocrystals and a colorant layer (CF-Yellow)
containing a yellow colorant in order to perform color correction
in consideration of the transmission of the excitation light. The
blue (B) pixel portion (blue color layer portion) is formed of a
color layer (NC-Blue) optionally containing blue-light-emitting
nanocrystals.
[0053] A preferred embodiment of the light conversion pixel layer
(NC-Red) containing the red-light-emitting nanocrystals, the light
conversion pixel layer (NC-Green) containing the
green-light-emitting nanocrystals, and the color layer (NC-Blue)
optionally containing the blue-light-emitting nanocrystals in the
light conversion layer 9 illustrated in FIG. 4 is the same as the
embodiment illustrated in FIG. 1, and thus the description is
omitted here. Although the red color layer portion, the green color
layer portion, and the blue color layer portion are illustrated as
being in contact with each other also in FIG. 4, a black matrix
serving as a light-shielding layer may be disposed therebetween in
order to prevent color mixing.
[0054] In the case where light having a main peak at or near 450 nm
(light having a blue emission spectrum) is emitted from the
electroluminescent layer 12, preferably, a colorant layer
containing a blue colorant (i.e., a blue color filter) is disposed
on one surface therebetween because the entry of unwanted light
from the outside can be prevented to inhibit a deterioration in
image quality. An example of a layer structure including the light
conversion layer 9 having the two-layer structure and the blue
color filter serving as essential elements is a structure
illustrated in FIG. 5.
[0055] FIG. 5 is an enlarged schematic view illustrating an example
of the light conversion layer 9 according to the present invention.
The light conversion layer 9 includes a red color layer R, a green
color layer G, and a blue color layer B. The red (R) pixel portion
R (red color layer R) includes a colorant layer (i.e., a red color
filter) CF-Red containing a red colorant, a light conversion pixel
layer (NC) containing a red-light-emitting nanocrystals, and a
colorant layer CFL (blue color filter CF-Blue) containing a blue
colorant. The green (G) pixel portion (green color layer G)
includes a colorant layer (i.e., a green color filter) CF-Green
containing a green colorant, a light conversion pixel layer (NC)
containing a green-light-emitting nanocrystals, and a colorant
layer CFL (blue color filter CF-Blue) containing a blue colorant.
The blue (B) pixel portion (blue color layer B) includes a
transparent rein layer and/or a color layer CFL (i.e., a blue color
filter) containing a blue colorant, a layer (NC) optionally
containing light-emitting nanocrystals, and a colorant layer CFL
(blue color filter) containing a blue colorant. A black matrix
serving as a light-shielding layer is disposed between the red
color layer, the green color layer, and the blue color layer.
[0056] Accordingly, the light conversion layer 9 has a stack having
a three-layer structure in which the (blue) color filter layer CFL,
the layer (NCL) containing the light-emitting nanocrystals NC, and
the red (R), green (G), or blue (B) color filter provided with the
three-primary pixel of the red (R), green (G), or blue (B) are
stacked in this order. However, the color filter layer CFL may be
eliminated, as needed. In place of the colorant layer (i.e., green
color filter) CF-Green containing the green colorant, a colorant
layer (i.e., yellow color filter) containing a yellow colorant may
be used for the purpose of color adjustment.
[0057] Each of the red color layer R, the green color layer G, and
the blue color layer B may appropriately contain a colorant, as
needed. The layer (NCL) containing the light-emitting nanocrystals
NC may contain colorants corresponding to the colors.
[0058] In the above structure, a portion of light (excitation
light, for example, blue light) from the electroluminescent layer
12, the portion having not been absorbed by the light-emitting
nanocrystals, can be absorbed by the color filter of each color and
the blue color filter layer CFL disposed on one surface. Thus, the
remaining excitation light can be inhibited or prevented from
passing through the light conversion layer. Also in FIG. 5, the
blue color filter is disposed as a color filter layer CFL because
light having a main peak at or near 450 nm (light having a blue
emission spectrum) is assumed to be used as light from the
electroluminescent layer 12. However, the color of the color filter
layer is appropriately changed in accordance with the type of light
source used.
[0059] FIG. 6 is a schematic cross-sectional view illustrating the
light-emitting device 100 according to another embodiment of the
present invention. The structure according to the embodiment
illustrated in FIG. 6 has the same structure as in FIG. 1, except
for the light conversion layer 9; thus, the description is omitted
here. The light conversion layer 9 according to the embodiment
illustrated in FIG. 6 has two layers: a layer containing
light-emitting nanocrystals and a color filter stacked.
Specifically, in the light conversion layer 9, a red (R) pixel
portion (red color layer portion) has a two-layer structure
including a layer (NCL) containing a light-emitting nanocrystals
and a colorant layer containing a red colorant, a green (G) pixel
portion (green color layer portion) has a two-layer structure
including the layer (NC) containing the light-emitting nanocrystals
and a colorant layer containing a green colorant, and a blue (B)
pixel portion (blue color layer portion) has a two-layer structure
including the layer (NC) containing the light-emitting nanocrystals
and a colorant layer containing a blue colorant.
[0060] In this case, the light-emitting nanocrystals in the layer
containing the light-emitting nanocrystals NC preferably contain
one or two selected from the group consisting of
blue-light-emitting nanocrystals that absorb incident light (light
from the light source, preferably blue light) to emit blue light, a
green-light-emitting nanocrystals that absorb incident light (light
from the light source, preferably blue light) to emit green light,
and a red-light-emitting nanocrystals that absorb incident light
(light from the light source, preferably blue light) to emit red
light. Also in this embodiment, a black matrix may be disposed in
order to prevent color mixing between the color layers.
[0061] In the embodiment illustrated in FIG. 6, a blue color filter
is preferably disposed on one surface of the light conversion layer
9 adjacent to the light-emitting layer because the entry of
unwanted light can be prevented to inhibit a deterioration in image
quality. FIG. 7 illustrates the structure of the light conversion
layer 9 including the blue color filter according to a modified
embodiment.
[0062] FIG. 7 is a schematic cross-sectional view illustrating the
light-emitting device 100 according to another embodiment of the
present invention. The embodiment illustrated in FIG. 7 differs
from the embodiment illustrated in FIG. 6 in that the colorant
layer (i.e., blue color filter) containing the blue colorant is
disposed on one surface; thus, the description is omitted here.
[0063] The light conversion layer, the electron injection layer,
the electron transport layer, the light-emitting layer, the hole
transport layer, and the hole injection layer, which are main
constituent elements of the light-emitting device according to the
present invention, will be described in detail below.
"Light Conversion Layer"
[0064] The light conversion layer according to the present
invention will be described in detail below. Regarding the
constituent elements of each of the pixel portions of the light
conversion layer, the pixel portion contains the light-emitting
nanocrystal as an indispensable component and may contain a resin
component and, if necessary, a molecule, a known additive, and
another colorant having an affinity for the light-emitting
nanocrystal. As described above, a black matrix is preferably
disposed at boundary portions between the pixel layers in view of
contrast.
(Light-Emitting Nanocrystal)
[0065] The light conversion layer according to the present
invention contains the light-emitting nanocrystals. The term
"nanocrystals" used in the present specification refers to
particles each having at least one dimension with a length of,
preferably, 100 nm or less. The nanocrystals may have any geometric
shape and may be symmetrical or asymmetrical. Specific examples of
the shape of the nanocrystals include long slender shapes, rod-like
shapes, circular shapes (spherical shapes), elliptical shapes,
pyramidal shapes, disc shapes, branched shapes, mesh-like shapes,
and irregular shapes. In some embodiments, the nanocrystals are
preferably quantum dots or quantum rods.
[0066] Each of the light-emitting nanocrystals preferably includes
a core containing at least one first semiconductor material; and a
shell covering the core and containing a second semiconductor
material identical to or different from that of the core.
[0067] Thus, the light-emitting nanocrystal is formed of the core
containing at least the first semiconductor material and the shell
containing the second semiconductor material, and the first
semiconductor material and the second semiconductor material may be
the same or different. The core and/or shell may contain a third
semiconductor material other than the first semiconductor and/or
the second semiconductor. The expression "covering the core" used
here indicates that at least part of the core may be covered.
[0068] Additionally, the light-emitting nanocrystal preferably
includes a core containing at least one first semiconductor
material, a first shell covering the core and containing a second
semiconductor material identical to or different from that of the
core, and, if necessary, a second shell covering the first shell
and containing a third semiconductor material identical to or
different from that of the first shell.
[0069] Accordingly, the light-emitting nanocrystal according to the
present invention preferably has at least one of the three
structures: a structure including a core containing a first
semiconductor material and a shell covering the core and containing
a second semiconductor material identical to the first
semiconductor material, i.e., a structure composed of one or two or
more semiconductor materials (=a structure consisting only of a
core (also referred to as a "core structure")); a core-shell
structure such as a structure including a core containing a first
semiconductor material and a shell covering the core and containing
a second semiconductor material different from that of the core;
and a core-shell-core structure such as a structure including a
core containing a first semiconductor material, a first shell
covering the core and containing a semiconductor material different
from that of the core, and a second shell covering the first shell
and containing a third semiconductor material different from that
of the first shell.
[0070] The light-emitting nanocrystal according to the present
invention preferably has three structures: the core structure, the
core-shell structure, and the core-shell-core structure, as
described above. In this case, the core may be composed of a mixed
crystal containing two or more semiconductor materials (for
example, CdSe+CdS or CIS+ZnS). The shell may also be composed of a
mixed crystal containing two or more semiconductor materials.
[0071] In the light conversion layer according to the present
invention, the light-emitting nanocrystal may be in contact with a
molecule (i.e., a ligand) having an affinity for the light-emitting
nanocrystal.
[0072] The molecule having an affinity is a low-molecular-weight
compound or a polymer having a functional group with an affinity
for the light-emitting nanocrystal. The functional group having an
affinity is not particularly limited and is preferably a group
containing one element selected from the group consisting of
nitrogen, oxygen, sulfur, and phosphorus. Examples thereof include
organic sulfur groups, organic phosphorus groups, a pyrrolidone
group, a pyridine group, an amino group, an amide group, an
isocyanate group, a carbonyl group, and a hydroxy group.
[0073] The semiconductor material according to the present
invention is preferably one or two or more selected from the group
consisting of II-VI group semiconductors, III-V group
semiconductors, I-III-VI group semiconductors, group IV
semiconductors, and I-II-IV-VI group semiconductors. Preferred
examples of the first semiconductor material, the second
semiconductor material, and the third semiconductor material
according to the present invention are the same as the
semiconductor materials described above.
[0074] Specifically, the semiconductor material according to the
present invention is at least one or more selected from the group
consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe,
HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe,
HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe,
CdHgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe,
HgZnSeS, HgZnSeTe, HgZnSTe; GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs,
AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP,
AlNAs, AINSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb,
GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs,
GaInNSb, GaInPAs, GaInPSb, InAINP, InAlNAs, InAlNSb, InAlPAs,
InAlPSb; SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe,
PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe,
SnPbSTe; SiC, SiGe, AgInSe.sub.2, CuGaSe.sub.2, CuInS.sub.2,
CuGaS.sub.2, CuInSe.sub.2, AgInS.sub.2, AgGaSe.sub.2, AgGaS.sub.2,
C, Si, and Ge. These compound semiconductors may be used alone or
in combination as a mixture of two or more. The semiconductor
material according to the present invention is preferably at least
one or more selected from the group consisting of CdS, CdSe, CdTe,
ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, InP, InAs, InSb, GaP, GaAs,
GaSb, AgInS.sub.2, AgInSe.sub.2, AgInTe.sub.2, AgGaS.sub.2,
AgGaSe.sub.2, AgGaTe.sub.2, CuInS.sub.2, CuInSe.sub.2,
CuInTe.sub.2, CuGaS.sub.2, CuGaSe.sub.2, CuGaTe.sub.2, Si, C, Ge,
and Cu.sub.2ZnSnS.sub.4. These compound semiconductors may be used
alone or in combination as a mixture of two or more.
[0075] The light-emitting nanocrystals according to the present
invention preferably contain at least one nanocrystal selected from
the group consisting of red-light-emitting nanocrystals that emit
red light, green-light-emitting nanocrystals that emit green light,
and blue-light-emission nanocrystals that emit blue light.
Typically, the emission color of the light-emitting nanocrystals
depends on the particle size in accordance with the solution of the
Schrodinger wave equation in a square-well potential model and also
depends on the energy gap of the light-emitting nanocrystals. Thus,
the emission color is selected by controlling the light-emitting
nanocrystals used and the particle size thereof.
[0076] The upper limit of the peak wavelength of the fluorescence
spectrum of the red-light-emitting nanocrystals that emit red light
in the present invention is preferably 665 nm, 663 nm, 660 nm, 658
nm, 655 nm, 653 nm, 651 nm, 650 nm, 647 nm, 645 nm, 643 nm, 640 nm,
637 nm, 635 nm, 632 nm, or 630 nm. The lower limit of the peak
wavelength is preferably 628 nm, 625 nm, 623 nm, 620 nm, 615 nm,
610 nm, 607 nm, or 605 nm.
[0077] The upper limit of the peak wavelength of the fluorescence
spectrum of the green-light-emitting nanocrystals that emit green
light in the present invention is preferably 560 nm, 557 nm, 555
nm, 550 nm, 547 nm, 545 nm, 543 nm, 540 nm, 537 nm, 535 nm, 532 nm,
or 530 nm. The lower limit of the peak wavelength is preferably 528
nm, 525 nm, 523 nm, 520 nm, 515 nm, 510 nm, 507 nm, 505 nm, 503 nm,
or 500 nm.
[0078] The upper limit of the peak wavelength of the fluorescence
spectrum of the blue-light-emitting nanocrystals that emit blue
light in the present invention is preferably 480 nm, 477 nm, 475
nm, 470 nm, 467 nm, 465 nm, 463 nm, 460 nm, 457 nm, 455 nm, 452 nm,
or 450 nm. The lower limit of the peak wavelength is preferably 450
nm, 445 nm, 440 nm, 435 nm, 430 nm, 428 nm, 425 nm, 422 nm, or 420
nm.
[0079] A semiconductor material used for the red-light-emitting
nanocrystals that emit red light in the present invention
preferably has a peak emission wavelength of 635 nm.+-.30 nm. A
semiconductor material used for the green-light-emitting
nanocrystals that emit green light preferably has a peak emission
wavelength of 530 nm.+-.30 nm. A semiconductor material used for
the blue-light-emission nanocrystals that emit blue light
preferably has a peak emission wavelength of 450 nm.+-.30 nm.
[0080] The lower limit of the fluorescence quantum yield of the
light-emitting nanocrystals according to the present invention, in
order of preference, is 40% or more, 30% or more, 20% or more, and
10% or more.
[0081] The upper limit of the full width at half maximum of the
fluorescence spectrum of the light-emitting nanocrystals according
to the present invention, in order of preference, is 60 nm or less,
55 nm or less, 50 nm or less, and 45 nm or less.
[0082] The upper limit of the particle size (primary particles) of
the red-light-emitting nanocrystals according to the present
invention, in order of preference, is 50 nm or less, 40 nm or less,
30 nm or less, and 20 nm or less.
[0083] The upper limit of the peak wavelength of the
red-light-emitting nanocrystals according to the present invention
is 665 nm, and the lower limit thereof is 605 nm. A compound and
its particle size are selected so as to obtain the peak wavelength.
The upper limit of the peak wavelength of the green-light-emitting
nanocrystals is 560 nm, and the lower limit thereof is 500 nm. The
upper limit of the peak wavelength of the blue-light-emission
nanocrystals is 420 nm, and the lower limit thereof is 480 nm.
Compounds and the particle size thereof are selected so as to
obtain the peak wavelengths.
[0084] The light-emitting device or the image display apparatus
according to the present invention includes at least one pixel. The
color of the pixel is obtained by three adjacent pixels. The pixels
contain different nanocrystals that emit colors of light: red (for
example, light-emitting nanocrystals composed of CdSe, rod-like
light-emitting nanocrystals composed of CdSe, rod-like
light-emitting nanocrystals having a core-shell structure in which
the shell portion is composed of CdS and the inner core portion is
composed of CdSe, rod-like light-emitting nanocrystals having a
core-shell structure in which the shell portion is composed of CdS
and the inner core portion is composed of ZnSe, light-emitting
nanocrystals having a core-shell structure in which the shell
portion is composed of CdS and the inner core portion is composed
of CdSe, light-emitting nanocrystals having a core-shell structure
in which the shell portion is composed of CdS and the inner core
portion is composed of ZnSe, light-emitting nanocrystals composed
of a mixed crystal of CdSe and ZnS, rod-like light-emitting
nanocrystals composed of a mixed crystal of CdSe and ZnS,
light-emitting nanocrystals composed of InP, rod-like
light-emitting nanocrystals composed of InP, light-emitting
nanocrystals composed of a mixed crystal of CdSe, rod-like
light-emitting nanocrystals composed of a mixed crystal of CdSe and
CdS, light-emitting nanocrystals composed of a mixed crystal of
ZnSe and CdS, or rod-like light-emitting nanocrystals composed of a
mixed crystal of ZnSe and CdS); green (light-emitting nanocrystals
composed of CdSe, rod-like light-emitting nanocrystals composed of
CdSe, light-emitting nanocrystals composed of a mixed crystal of
CdSe and ZnS, or rod-like light-emitting nanocrystals composed of a
mixed crystal of CdSe and ZnS); and blue (light-emitting
nanocrystals composed of ZnSe, rod-like light-emitting nanocrystals
composed of ZnSe, light-emitting nanocrystals composed of ZnS,
rod-like light-emitting nanocrystals composed of ZnS,
light-emitting nanocrystals having a core-shell structure in which
the shell portion is composed of ZnSe and the inner core portion is
composed of ZnS, rod-like light-emitting nanocrystals having a
core-shell structure in which the shell portion is composed of ZnSe
and the inner core portion is composed of ZnS, light-emitting
nanocrystals composed of CdS, or rod-like light-emitting
nanocrystals composed of CdS). The light conversion layer may
contain another color (for example, yellow), as needed.
Furthermore, different colors obtained from adjacent four or more
pixels may also be used.
[0085] The average particle size (primary particles) of the
light-emitting nanocrystals according to the present invention in
this specification can be measured by TEM observation. Typical
examples of a method for measuring the average particle size of
nanocrystals include a light scattering method, a particle size
measurement method by sedimentation with a solvent, and a method in
which particles are directly observed with an electron microscope
and average particle size is actually measured. The light-emitting
nanocrystals are easily degraded by, for example, water. In the
present invention, thus, a method is preferred in which
freely-selected multiple crystals are directly observed with a
transmission electron microscope (TEM) or scanning electron
microscope (SEM), the particle sizes of the particles are
calculated from the ratio of the length of the major axis to the
length of the minor axis in a two-dimensional projection image, and
the average thereof is determined. In the present invention, thus,
the average particle size is calculated by the method. The term
"primary particles" of the light-emitting nanocrystals refers to
single crystals having a size of several to several tens of
nanometers or crystallites similar thereto. The size and shape of
the primary particles of the light-emitting nanocrystals seems to
depend on, for example, the chemical composition, structure,
production method, and production conditions of the primary
particles.
[0086] The light conversion layer in the present invention
preferably contains a resin component that appropriately disperses
and stabilizes the light-emitting nanocrystals in addition to the
light-emitting nanocrystals.
[0087] The resin component is preferably an alkali-developable
polymer derived from a photopolymerizable compound because the
light conversion layer is produced mainly by a photolithography
method. Specific examples thereof include polymers derived from
bifunctional monomers such as 1,6-hexanediol diacrylate, ethylene
glycol diacrylate, neopentyl glycol diacrylate, triethylene glycol
diacrylate, bis(acryloxyethoxy)bisphenol A, and 3-methylpentanediol
diacrylate; polymers derived from relatively-low-molecular-weight
multifunctional monomers such as trimethylolpropane triacrylate,
pentaerythritol triacrylate,
tris[2-(meth)acryloyloxyethyl)isocyanurate, dipentaerythritol
hexaacrylate, and dipentaerythritol pentaacrylate; and polymers
derived from relatively-large-molecular-weight multifunctional
monomers such as polyester acrylate, polyurethane acrylate, and
polyether acrylate.
[0088] A thermoplastic resin may be partially used in combination
with the polymer. Examples of the thermoplastic resin include
urethane-based resins, acrylic resins, polyamide-based resins,
polyimide-based resins, styrene-maleic acid-based resins, and
styrene-maleic anhydride resins.
[0089] If necessary, the light conversion layer according to the
present invention may further contain known additives such as a
polymerization initiator, a catalyst, and a scattering agent, e.g.,
alumina, silica, titanium oxide beads, zeolite, or zirconia, in
addition to the transparent resin and the light-emitting
nanocrystals.
(Colorant)
[0090] The light conversion layer according to the present
invention includes pixel portions of three colors of red (R), green
(G), and blue (B) and, if necessary, may contain a colorant. As the
colorant, a known colorant may be used. For example, preferably,
the red (R) pixel portion contains a diketopyrrolopyrrole pigment
and/or an anionic red organic dye, the green (G) pixel portion
contains at least one selected from the group consisting of
halogenated copper phthalocyanine pigments, phthalocyanine-based
green dyes, and mixtures of phthalocyanine-based blue dyes and
azo-based yellow organic dyes, and the blue (B) pixel portion
contains an B-type copper phthalocyanine pigment and/or a cationic
blue organic dye.
[0091] A preferred colorant optionally added, together with the
light-emitting nanocrystals, in the red color layer according to
the present invention preferably contains a diketopyrrolopyrrole
pigment and/or an anionic red organic dye. As the
diketopyrrolopyrrole pigment, specifically, one or two or more
selected from C.I. Pigment Red 254, 255, 264, and 272 and Orange 71
and 73 are preferred. One or two or more selected from Red 254,
255, 264, and 272 are more preferred. C.I. Pigment Red 254 is
particularly preferred. As the anionic red organic dye,
specifically, one or two or more selected from C.I. Solvent Red 124
and Acid Red 52 and 289 are preferred. C.I. Solvent Red 124 is
particularly preferred.
[0092] Preferably, the red color layer according to the present
invention further contains, as a colorant, at least one organic dye
or pigment selected from the group consisting of C.I. Pigment Red
177, 242, 166, 167, and 179, C.I. Pigment Orange 38 and 71, C.I.
Pigment Yellow 150, 215, 185, 138, and 139, C.I. Solvent Red 89,
C.I. Solvent Orange 56, C.I. Solvent Yellow 21, 82, 83:1, 33, and
162.
[0093] A preferred colorant optionally added, together with the
light-emitting nanocrystals, in the green color layer according to
the present invention preferably contains at least one selected
from the group consisting of halogenated metal phthalocyanine
pigments, phthalocyanine-based green dyes, and mixtures of
phthalocyanine-based blue dyes and azo-based yellow organic dyes.
As the halogenated metal phthalocyanine pigments, the following two
groups of halogenated metal phthalocyanine pigments are
exemplified.
(First Group)
[0094] Halogenated metal phthalocyanine pigments each containing,
as a central metal, a metal selected from the group consisting of
Al, Si, Sc, Ti, V, Mg, Fe, Co, Ni, Zn, Ga, Ge, Y, Zr, Nb, In, Sn,
and Pb, 8 to 16 halogen atoms per phthalocyanine molecule being
bonded to the benzene rings of the phthalocyanine molecule, in
which when the central metal is trivalent, any of one halogen atom,
a hydroxy group, and a sulfonic group (--SO.sub.3H) is bonded to
the central metal and in which when the central metal is a
tetravalent metal, any of one oxygen atom, two halogen atoms that
may be the same or different, a hydroxy group, and a sulfonic group
is bonded to the central metal.
(Second Group)
[0095] Pigments composed of halogenated metal phthalocyanine dimers
each having a structural unit containing two halogenated metal
phthalocyanine molecules having central metals composed of
trivalent metals each selected from the group consisting of Al, Sc,
Ga, Y, and In, 8 to 16 halogen atoms per phthalocyanine molecule
being bonded to the benzene rings of the phthalocyanine molecule,
the central metals of the structural unit being bonded to each
other with a divalent atomic group selected from the group
consisting of an oxygen atom, a sulfur atom, sulfinyl (--SO--), and
sulfonyl (--SO.sub.2--) provided therebetween.
[0096] In the halogenated metal phthalocyanine pigment used in the
present invention, the halogen atoms bonded to the benzene rings
may be all the same or different. Different halogen atoms may be
bonded to one benzene ring.
[0097] The halogenated metal phthalocyanine pigment, in which 9 to
15 bromine atoms among 8 to 16 halogen atoms per phthalocyanine
molecule are bonded to the benzene rings of the phthalocyanine
molecule, used in the present invention appears light yellowish
green and is most suitable for use in the green pixel portion of
the color filter. The halogenated metal phthalocyanine used in the
present invention is insoluble or poorly soluble in water and
organic solvents. Pigments that are not subjected to finishing
treatment (also referred to as "crude pigments") and pigments that
are subjected to finishing treatment are also included in the
halogenated metal phthalocyanine used in the present invention.
[0098] The halogenated metal phthalocyanine pigments belonging to
the first and second groups can be represented by general formula
(PIG-1):
##STR00001##
[0099] The halogenated metal phthalocyanine pigments belonging to
the first group and represented by general formula (PIG-1) are
described below.
[0100] In general formula (PIG-1), X.sub.1 to X.sub.16 each
represent a hydrogen atom, a chlorine atom, a bromine atom, or an
iodine atom. Four X atoms bonded to one benzene ring may be the
same or different. Among X.sub.1 to X.sub.16 bonded to four benzene
rings, 8 to 16 atoms are each a chlorine atom, a bromine atom, or
an iodine atom. M represents a center metal. In the halogenated
metal phthalocyanine pigments having the same Y described below and
the same number m thereof, a pigment in which the total of chlorine
atoms, bromine atoms, and iodine atoms in 16 X.sub.1 to X.sub.16 is
less than 8 is blue. Similarly, in a pigment in which the total of
chlorine atoms, bromine atoms, and iodine atoms in 16 X.sub.1 to
X.sub.16 is 8 or more, yellow is deeper as the total value is
larger. Y bonded to the central metal M is a monovalent atomic
group selected from the group consisting of a halogen atom of
fluorine, chlorine, bromine, or iodine, an oxygen atom, a hydroxy
group, and a sulfonic group, and m is the number of Y bonded to the
central metal M and is an integer of 0 to 2.
[0101] The value of m is determined in accordance with the valence
of the central metal M. In the case where the central metal M is a
trivalent metal such as Al, Sc, Ga, Y, or In, m=1, and one group
selected from the group consisting of fluorine, chlorine, bromine,
iodine, a hydroxy group, and a sulfonic group is bonded to the
central metal. In the case where the central metal M is a
tetravalent metal such as Si, Ti, V, Ge, Zr, or Sn, m=2. In this
case, one oxygen atom is bonded to the central metal, or two groups
selected from the group consisting of fluorine, chlorine, bromine,
iodine, a hydroxy group, and a sulfonic group are bonded to the
central metal. In the case where the central metal M is a divalent
metal such as Mg, Fe, Co, Ni, Zn, Zr, Sn, or Pb, Y is not
present.
[0102] The halogenated metal phthalocyanine pigments belonging to
the second group and represented by general formula (PIG-1) are
described below.
[0103] In general formula (PIG-1), X.sub.1 to X.sub.16 are as
defined above. The central metal M is a trivalent metal selected
from the group consisting of Al, Sc, Ga, Y, and In, and m is 1. Y
represents an atomic group illustrated below.
##STR00002##
[0104] In the chemical structure of the atomic group Y, the central
metal M is as defined above. X.sub.17 to X.sub.32 are as defined
for X.sub.1 to X.sub.16 in general formula (PIG-1). A is a divalent
atomic group selected from the group consisting of an oxygen atom,
a sulfur atom, sulfinyl (--SO--), and sulfonyl (--SO.sub.2--). M in
general formula (PIG-1) is bonded to M in the atomic group Y with
the divalent atomic group A provided therebetween.
[0105] The halogenated metal phthalocyanine pigments belonging to
the second group are halogenated metal phthalocyanine dimers each
having a structural unit containing two halogenated metal
phthalocyanine molecules that are bonded to each other with the
divalent atomic group provided therebetween.
[0106] Specific examples of the halogenated metal phthalocyanine
pigments represented by general formula (PIG-1) include the
following items (1) to (4).
(1) Halogenated metal phthalocyanine pigments such as halogenated
tin phthalocyanine pigments, halogenated nickel phthalocyanine
pigments, and halogenated zinc phthalocyanine pigments, each of the
halogenated metal phthalocyanine pigments containing, as a central
metal, a divalent metal selected from the group consisting of Mg,
Fe, Co, Ni, Zn, Zr, Sn, and Pb, 8 to 16 halogen atoms being bonded
to four benzene rings per phthalocyanine molecule. Among these, a
chlorinated brominated zinc phthalocyanine pigment is C.I. Pigment
Green 58, which is particularly preferred. (2) Halogenated metal
phthalocyanine pigments such as halogenated chloroaluminum
phthalocyanines, each of the halogenated metal phthalocyanine
pigments containing, as a central metal, a trivalent metal selected
from the group consisting of Al, Sc, Ga, Y, and In, the central
metal being bonded to one halogen atom, a hydroxy group, or a
sulfonic group, 8 to 16 halogen atoms being bonded to four benzene
rings per phthalocyanine molecule. (3) Halogenated metal
phthalocyanine pigments such as halogenated oxytitanium
phthalocyanines and halogenated oxyvanadium phthalocyanine, each of
the halogenated metal phthalocyanine pigments containing, as a
central metal, a tetravalent metal selected from the group
consisting of Si, Ti, V, Ge, Zr, and Sn, the central metal being
bonded to one oxygen atom, two halogen atoms that may be the same
or different, a hydroxy group, or a sulfonic group, 8 to 16 halogen
atoms being bonded to four benzene rings per phthalocyanine
molecule. (4) Pigments composed of halogenated metal phthalocyanine
dimers such as halogenated .mu.-oxo-aluminum phthalocyanines and
halogenated .mu.-thio-aluminum phthalocyanine dimers, each of the
halogenated metal phthalocyanine dimers each having a structural
unit containing two halogenated metal phthalocyanine molecules
having central metals composed of trivalent metals each selected
from the group consisting of Al, Sc, Ga, Y, and In, 8 to 16 halogen
atoms being bonded to four benzene rings per phthalocyanine
molecule, the central metals of the structural unit being bonded to
each other with a divalent atomic group selected from the group
consisting of an oxygen atom, a sulfur atom, sulfinyl, and sulfonyl
(--SO.sub.2--) provided therebetween.
[0107] Regarding other colorants, preferably, a mixture of C.I.
Solvent Blue 67 and C.I. Solvent Yellow 162, or C.I. Pigment Green
7 and/or 36 is optionally contained in the green color layer.
[0108] Preferably, the green color layer according to the present
invention further contains, as a colorant, at least one organic dye
or pigment selected from the group consisting of C.I. Pigment
Yellow 150, 215, 185, and 138 and C.I. Solvent Yellow 21, 82, 83:1,
and 33.
[0109] A preferred colorant optionally added, together with the
light-emitting nanocrystals, in the blue color layer according to
the present invention preferably contains an 8-type copper
phthalocyanine pigment and/or a cationic blue organic dye. The
.epsilon.-type copper phthalocyanine pigment is C.I. Pigment Blue
15:6. Specifically, the cationic blue organic dye is preferably
C.I. Solvent Blue 2, 3, 4, 5, 6, 7, 23, 43, 72, and 124, and C.I.
Basic Blue 7 and 26, more preferably C.I. Solvent Blue 7 and Basic
Blue 7, particularly preferably C.I. Solvent Blue 7.
[0110] Preferably, the blue color layer according to the present
invention further contains, as a colorant, at least one organic dye
or pigment selected from the group consisting of C.I. Pigment Blue
1, C.I. Pigment Violet 23, C.I. Basic Blue 7, C.I. Basic Violet 10,
C.I. Acid Blue 1, 90, and 83, and C.I. Direct Blue 86.
[0111] In the case where the light conversion layer according to
the present invention contains a yellow (Y) pixel portion (yellow
color layer), the yellow color layer preferably contains, as a
colorant, at least one yellow organic dye or pigment selected from
the group consisting of C.I. Pigment Yellow 150, 215, 185, 138, and
139, C.I. Solvent Yellow 21, 82, 83:1, 33, and 162.
[0112] In the light conversion layer according to the present
invention, the upper limit of the light-emitting nanocrystal
content with respect to the transparent resin is preferably 80
parts by mass, 70 parts by mass, 60 parts by mass, or 50 parts by
mass based on 100 parts by mass of the transparent resin. The lower
limit of the light-emitting nanocrystal content is preferably 1.0
part by mass, 3.0 parts by mass, 5.0 parts by mass, or 10.0 parts
by mass based on 100 parts by mass of the transparent resin. In the
case where multiple types of light-emitting nanocrystals are
contained in the light conversion layer, the content described
above indicates the total content.
(Color Filter)
[0113] The light conversion layer according to the present
invention is preferably formed of a stack in which a layer (NC)
containing the light-emitting nanocrystals and a color filter are
stacked (for example, FIG. 10). Specifically, the light conversion
layer preferably includes a red color layer R, a green color layer
G, and a blue color layer B. In this case, the red (R) pixel
portion R (red color layer portion R) preferably includes a layer
(NC) containing red-light-emitting nanocrystals and a colorant
layer (CF-Red) containing a red colorant. The green (R) pixel
portion (green color layer portion G) preferably includes a layer
(NC) containing green-light-emitting nanocrystals and a colorant
layer (CF-Green) containing a green colorant or a colorant layer
(yellow color layer) containing a yellow colorant. The blue (R)
pixel portion (blue color layer potion B) preferably include a
colorant layer (CF-Blue, blue colorant-containing layer) containing
a blue colorant and/or a transparent resin layer and, if necessary,
a layer (NC) containing blue-light-emitting nanocrystals. In the
present invention, a colorant-containing color filter such as the
colorant layer (CF-Green or CF-Red) stacked on the light conversion
pixel layer illustrated in FIGS. 4 to 7, the color filter (CFL)
illustrated in FIGS. 5 to 7, or the blue color filter (CF-Blue)
illustrated in FIGS. 3, 5, and so forth may be appropriately
used.
[0114] The color filter is preferably formed with the colorant. For
example, preferably, the red (R) color filter contains a
diketopyrrolopyrrole pigment and/or an anionic red organic dye, the
green (G) color filter contains at least one selected from the
group consisting of halogenated copper phthalocyanine pigments,
phthalocyanine-based green dyes, and mixtures of
phthalocyanine-based blue dyes and azo-based yellow organic dyes,
and the blue (B) color filter contains an B-type copper
phthalocyanine pigment and/or a cationic blue organic dye.
[0115] The color filter may contain, for example, the transparent
resin, a photocurable compound, and a dispersant, as needed.
Regarding a method for producing the color filter, the color filter
may be formed by, for example, a known photolithography method.
(Method for Producing Light Conversion Layer)
[0116] The light conversion layer may be formed by a known method.
A typical method for forming a pixel portion is a photolithography
method, which is described as follows: A photocurable composition
containing light-emitting nanocrystals described below is applied
to a surface of a conventional color filter transparent substrate
on which a black matrix is disposed. After drying by heating
(prebaking), pattern exposure is performed by irradiation with
ultraviolet radiation using a photomask. After a photocurable
compound disposed at a position corresponding to a pixel portion is
cured, an unexposed portion is developed with a developer. A
non-pixel portion is removed, and the pixel portion is fixed to the
transparent substrate. In this method, a pixel portion composed of
the cured colored film of the photocurable composition containing
the light-emitting nanocrystals is formed on the transparent
substrate.
[0117] Photocurable compositions described below are prepared for
red (R) pixels, green (G) pixels, blue (B) pixels, and, if
necessary, other color pixels such as yellow (Y) pixels. The above
operation can be repeated to produce a light conversion layer
having a color pixel portion including the red (R) pixels, the
green (G) pixels, the blue (B) pixels, and the yellow (Y) pixels
located at predetermined positions.
[0118] Examples of a method for applying the photocurable
composition containing the light-emitting nanocrystals described
below to a transparent substrate such as glass include a spin
coating method, a roll coating method, and an inkjet method.
[0119] The drying conditions of the film of the photocurable
composition containing the light-emitting nanocrystals applied to
the transparent substrate vary depending on, for example, the type
of component and the mixing ratio and are usually at about
50.degree. C. to about 150.degree. C. for about 1 to about 15
minutes. As light used for the photocuring of the photocurable
composition containing the light-emitting nanocrystals, ultraviolet
radiation or visible light in a wavelength range of 200 to 500 nm
is preferably used. Various light sources that emit light in the
wavelength range can be used.
[0120] Examples of the developing method include a liquid
deposition method, a dipping method, and a spray method. After
exposing and developing the photocurable composition, a transparent
substrate on which a required color pixel portion is formed is
washed with water and dried. The resulting color filter is
subjected to heat treatment (post baking) with a heating device
such as a hot plate or an oven at 90.degree. C. to 280.degree. C.
for a predetermined time. This removes a volatile component in the
colored coating film and allows the unreacted photocurable compound
remaining in the photocurable composition containing the
light-emitting nanocrystals to be thermally cured, thereby
completing the light conversion layer.
[0121] The colorant for the light conversion layer and the resin of
the present invention are used together with the light-emitting
nanocrystals of the present invention to prevent deterioration and
an increase in ion density (ID) due to blue light or ultraviolet
light, thus enabling an image display apparatus to solve display
defects such as voids to be provided.
[0122] A typical method for producing the photocurable composition
containing the light-emitting nanocrystals is as follows: The
light-emitting nanocrystals and an organic solvent are mixed
together. Molecules having an affinity thereto, a dispersant, and a
colorant (=a dye and/or pigment composition) are added thereto, as
needed. The mixture is stirred and dispersed so as to be uniform,
thereby preparing a dispersion for the formation of the pixel
portion of the light conversion layer. A photocurable compound and,
if necessary, a thermoplastic resin, a photopolymerization
initiator, and so forth are added thereto, thereby preparing a
light-emitting-nanocrystal-containing photocurable composition
containing the light-emitting nanocrystals.
[0123] Examples of the organic solvent used here include aromatic
solvents such as toluene, xylene, and methoxybenzene; acetate-based
solvents such as ethyl acetate, propyl acetate, butyl acetate,
propylene glycol monomethyl ether acetate, propylene glycol
monoethyl ether acetate, diethylene glycol methyl ether acetate,
diethylene glycol ethyl ether acetate, diethylene glycol propyl
ether acetate, and diethylene glycol butyl ether acetate;
propionate-based solvents such as ethoxyethyl propionate; alcoholic
solvents such as methanol and ethanol; ether-based solvents such as
butyl cellosolve, propylene glycol monomethyl ether, diethylene
glycol ethyl ether, and diethylene glycol dimethyl ether;
ketone-based solvents such as methyl ethyl ketone, methyl isobutyl
ketone, and cyclohexanone; aliphatic hydrocarbon-based solvents
such as hexane; nitrogen compound-based solvents such as
N,N-dimethylformamide, .gamma.-butyrolactam,
N-methyl-2-pyrrolidone, aniline, and pyridine; lactone-based
solvent such as .gamma.-butyrolactone; and carbamates such as a
methyl carbamate-ethyl carbamate (48:52) mixture.
[0124] Examples of the dispersant used here include dispersants
such as DISPERBYK 130, DISPERBYK 161, DISPERBYK 162, DISPERBYK 163,
DISPERBYK 170, DISPERBYK 171, DISPERBYK 174, DISPERBYK 180,
DISPERBYK 182, DISPERBYK 183, DISPERBYK 184, DISPERBYK 185,
DISPERBYK 2000, DISPERBYK 2001, DISPERBYK 2020, DISPERBYK 2050,
DISPERBYK 2070, DISPERBYK 2096, DISPERBYK 2150, DISPERBYK LPN21116,
and DISPERBYK LPN6919, available from BYK Chemie, Efka 46, Efka 47,
Efka 452, Efka LP4008, Efka 4009, Efka LP4010, Efka LP4050, LP4055,
Efka 400, Efka 401, Efka 402, Efka 403, Efka 450, Efka 451, Efka
453, Efka 4540, Efka 4550, Efka LP4560, Efka 120, Efka 150, Efka
1501, Efka 1502, and Efka 1503, available from Efka, Solsperse
3000, Solsperse 9000, Solsperse 13240, Solsperse 13650, Solsperse
13940, Solsperse 17000, 18000, Solsperse 20000, Solsperse 21000,
Solsperse 20000, Solsperse 24000, Solsperse 26000, Solsperse 27000,
Solsperse 28000, Solsperse 32000, Solsperse 36000, Solsperse 37000,
Solsperse 38000, Solsperse 41000, Solsperse 42000, Solsperse 43000,
Solsperse 46000, Solsperse 54000, and Solsperse 71000, available
from Lubrizol Corporation, Ajisper PB711, Ajisper PB821, Ajisper
PB822, Ajisper PB814, Ajisper PN411, and Ajisper PA111, available
from Ajinomoto Co., Inc., acrylic resins, urethane-based resins,
alkyd-based resins, natural rosin such as wood rosin, gum rosin,
and tall rosin, modified rosin such as polymerized rosin,
disproportionated rosin, hydrogenated rosin, oxidized rosin, and
maleated rosin, rosin derivatives such as rosin amines, limed
rosin, alkylene oxide adducts of rosin, alkyd adducts of rosin, and
rosin-modified phenol, which are water-insoluble liquid synthetic
resins at room temperature that may be contained. The addition of
the dispersant and the resin contributes to the inhibition of
flocculation, an improvement in the dispersion stability of a
pigment, and an improvement in the viscosity properties of a
dispersion.
[0125] An organic pigment derivative may also be contained as a
dispersion aid. Examples thereof include phthalimidomethyl
derivatives, sulfonic derivatives, N-(dialkylamino)methyl
derivatives, and N-(dialkylaminoalkyl)sulfonic acid amide
derivatives. Two or more different types of these derivatives may
be used in combination.
[0126] Examples of a thermoplastic resin used for the preparation
of a photocurable composition containing the light-emitting
nanocrystals include urethane-based resins, acrylic resins,
polyamide-based resins, polyimide-based resins, styrene-maleic acid
resins, and styrene-maleic anhydride resins.
[0127] Examples of the photocurable compound in the light-emitting
nanocrystals containing photocurable composition include
bifunctional monomers such as 1,6-hexanediol diacrylate, ethylene
glycol diacrylate, neopentyl glycol diacrylate, triethylene glycol
diacrylate, bis(acryloxyethoxy)bisphenol A, and 3-methylpentanediol
diacrylate; multifunctional monomers having relatively small
molecular weights, such as trimethylolpropane triacrylate,
pentaerythritol triacrylate,
tris[2-(meth)acryloyloxyethyl)isocyanurate, dipentaerythritol
hexaacrylate, and dipentaerythritol pentaacrylate; and
multifunctional monomers having relatively large molecular weights,
such as polyester acrylate, polyurethane acrylate, and polyether
acrylate.
[0128] Examples of the photopolymerization initiator include
acetophenone, benzophenone, benzyldimethylketal, benzoyl peroxide,
2-chlorothioxanthone, 1,3-bis(4'-azidobenzal)-2-propane,
1,3-bis(4'-azidobenzal)-2-propane-2'-sulfonic acid, and
4,4'-diazidostilbene-2,2'-disulfonic acid. Examples of a
commercially available photopolymerization initiator include
Irgacure (trade name)-184, Irgacure (trade name)-369 available from
BASF, Darocur (trade name)-1173, and Lucirin-TPO available from
BASF; Kayacure (trade name) DETX and Kayacure (trade name) OA,
available from Nippon Kayaku Co., Ltd.; Vicure 10 and Vicure 55
available from Stauffer; Trigonal PI available from Akzo; Sandoray
1000 available from Sandoz; Deap available from The Upjohn Company;
and Biimidazole available from Kurogane Kasei Co., Ltd.
[0129] A known photosensitizer may be used in combination with the
photopolymerization initiator. Examples of the photosensitizer
include amines, ureas, compounds containing sulfur atoms, compounds
containing phosphorus atoms, compounds containing chlorine atoms,
nitriles, and other compounds containing nitrogen atoms. These may
be used alone or in combination of two or more.
[0130] The photopolymerization initiator content is not
particularly limited and is, by mass, preferably in the range of
0.1% to 30% based on a compound having a photopolymerizable or
photocurable functional group. At less than 0.1%, the sensitivity
during photo-curing tends to decrease. At more than 30%, when a
coating film composed of a resist containing a pigment dispersed is
dried, the crystals of the photopolymerization initiator can
precipitate to degrade the physical properties of the coating
film.
[0131] The materials as described above are used. On a mass basis,
300 to 100,000 parts of an organic solvent and 1 to 500 parts of
molecules or a dispersant having an affinity based on 100 parts of
the light-emitting nanocrystals of the present invention are
stirred and dispersed uniformly, thereby preparing a dispersion.
Then 0.125 to 2,500 parts of the total of a thermoplastic resin and
a photocurable compound based on 100 parts of the pigment
dispersion, 0.05 to 10 parts of a photopolymerization initiator
based on 1 part of the photocurable compound, and, if necessary, an
organic solvent are stirred and dispersed uniformly, thereby
enabling a photocurable composition containing the light-emitting
nanocrystals to be prepared for the formation of a pixel
portion.
[0132] A known organic solvent or aqueous alkali solution may be
used as a developer. In particular, in the case where the
photocurable composition contains a thermoplastic resin or a
photocurable compound and where at least one of them has an acid
value or is soluble in alkali, washing with an aqueous alkali
solution is effective in forming a color filter pixel portion.
[0133] The method for producing the color pixel portions including
the R pixels, the G pixels, the B pixels, and the Y pixels by the
photolithography method has been described in detail. Regarding the
pixel portions formed from the composition containing the
light-emitting nanocrystals according to the present invention, the
color pixel portions may be formed by another method such as an
electrodeposition method, a transfer method, a micelle electrolytic
method, a photovoltaic electrodeposition (PVED) method, an inkjet
method, a reverse printing method, or a thermal curing method to
produce a light conversion layer.
"Electron Injection Layer"
[0134] As a material used for the electron injection layer
according to the present invention, a material having a low work
function can be used. Examples thereof include alkali metals such
as lithium and cesium, their oxides, their halides, and their
carbonates, alkaline-earth metals such as calcium, their oxides,
their halides, and their carbonates, Lewis bases such as magnesium
silver and magnesium oxide, and lithium-aluminum alloys. It is
believed that these materials can reduce a potential barrier formed
during electron injection from one electrode. As a material used
for the electron transport layer, a composite material having an
electron-donating ability (donor) may be used. Examples of the
electron-donating material include alkali-metal compounds such as
lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride
(CaF.sub.2), and lithium oxide (LiOx), alkaline-earth metal
compounds, rare-earth metal compounds such as erbium fluoride
(ErF.sub.3).
[0135] A composite material containing a mixture of an organic
compound (acceptor) and an electron-donating material (donor) may
be used for the electron injection layer according to the present
invention. As the electron donor, any material having an
electron-donating ability to the organic compound serving as an
acceptor may be used. Alkali metals, alkaline-earth metals,
rare-earth metals, and compounds containing these metals are
preferred. Specific examples thereof include lithium, cesium,
magnesium, calcium, erbium, ytterbium, and compounds containing
these metals. Alkali metal oxides and alkaline-earth metal oxides
are preferred. Lewis bases such as lithium oxide, calcium oxide,
and magnesium oxide and barium oxide are more preferred. Organic
materials such as tetrathiafulvalene may be used. Regarding the
organic compound (acceptor), because an electron is given to the
organic compound by the electron-donating material (donor), the
composite material containing the mixture of the organic compound
(acceptor) and the electron-donating material (donor) has good
electron injection properties and good electron transport
properties. In this case, as the organic compound (acceptor), for
example, electron transport materials described below are
preferred.
"Electron Transport Layer"
[0136] As a material used for the electron transport layer
according to the present invention, a material whose electron
transport ability is higher than its hole transport ability is
preferably used. Examples thereof include .pi.-electron-deficient
heteroaromatic compounds such as nitrogen-containing heteroaromatic
compounds and metal complexes. Specific examples thereof include
metal complexes containing quinoline ligands, perylene ligands,
benzoquinoline ligands, oxazole ligands, and thiazole ligands,
fullerenes, oxadiazole derivatives, triazole derivatives,
phenanthroline derivatives, pyridine derivatives, bipyridine
derivatives, and pyrimidine derivatives.
[0137] More specific examples thereof include low-molecular-weight
compounds such as tris(8-quinolinolato)aluminum(III) (Alq),
tris(4-methyl-8-quinolinolato)aluminum(III) (Almq3),
bis(10-hydroxybenzo[h]quinolinato)beryllium(II),
bis(2-methyl-8-quinolinolato) (4-phenylphenolato)aluminum(III),
bis(8-quinolinolato)zinc(II),
bis[2-(2-benzooxazolyl)phenolato]zinc(II),
bis[2-(2-benzothiazolyl)phenolato]zinc(II),
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole,
1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene,
9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole,
3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole,
2,2',2'''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole),
2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole,
bathophenanthroline, bathocuproine,
2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline,
2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline,
2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline,
2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline,
7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline,
6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline,
diazines, e.g., 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine,
4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine, and
4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine,
2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-
-1,3,5-triazine, 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine,
1,3,5-tri[3-(3-pyridyl)phenyl]benzene, and
4,4'-bis(5-methylbenzoxazol-2-yl)stilbene. Furthermore, a polymer
such as poly(2,5-pyridinediyl),
poly[(9,9-dihexylfluoren-2,7-diyl)-co-(pyridin-3,5-diyl)], or
poly[(9,9-dioctylfluoren-2,7-diyl)-co-(2,2'-bipyridin-6,6'-diyl)]
may be used.
[0138] The electron transport layer according to the present
invention preferably has an average thickness of 7 nm to 300 nm.
The electron transport layer may be formed of a single layer or a
stack of two or more layers composed of the foregoing material, as
needed. A functional layer such as a hole-blocking layer that can
control electron transfer may be disposed between the electron
transport layer and the light-emitting layer.
[0139] The above structure is seemingly effective in inhibiting or
preventing a decrease in the lifetime of the light-emitting
device.
"Light-Emitting Layer"
[0140] The light-emitting layer 5 according to the present
invention preferably has the peak of an emission spectrum in the
blue wavelength region. The light-emitting layer may be formed of a
single layer or multiple layers including two or more layers
containing a light-emitting material described below. An example of
a structure including three light-emitting layers is a structure in
which one of the light-emitting layers emits light in the blue
wavelength region (420 nm or more and 480 nm or less), another
light-emitting layer emits light in the green wavelength region
(500 to 560 nm), and the other light-emitting layer emits light in
the red wavelength region (620 to 650 nm). In this case, a buffer
layer may be disposed between the blue light-emitting layer, the
green light-emitting layer, and the red light-emitting layer in
contact with the green light-emitting layer. An example of a
structure including two light-emitting layers is a structure in
which one of the light-emitting layers emits light in the blue
wavelength region (420 nm or more and 480 nm or less) and the other
light-emitting layer emits light in the yellow wavelength region
(570 to 590 nm). In this case, a buffer layer may be disposed
between the blue light-emitting layer and the yellow light-emitting
layer, as needed. In the case where the light-emitting layer is
formed of a single layer, the light-emitting layer preferably emits
light in the blue wavelength region (420 nm or more and 480 nm or
less), more preferably emits light in the blue wavelength region
(430 nm or more and 470 nm or less), even more preferably emits
light in the blue wavelength region (440 nm or more and 460 nm or
less).
[0141] In a particularly preferred embodiment of the present
invention, the light-emitting layer is formed of a single layer
that emits light in the blue wavelength region (420 nm or more and
480 nm or less). As described above, the color display method of
the present invention is preferably a display method in which a
light-emitting layer that emits blue light, a light conversion
layer that converts the blue light from the light-emitting layer
into green light, and a light conversion layer that converts the
blue light from the light-emitting layer into red light are
combined together to produce three colors. The blue color obtained
from the blue-light-emitting layer is used as a blue color, and the
light-emitting nanocrystals that differ in particle size and
material are used to produce the green color and the red color,
thereby producing three colors.
[0142] The light-emitting layer according to the present invention
can be formed by a physical vapor deposition (PVD) method such as a
vacuum evaporation method, a printing method such as a screen
printing method or an inkjet printing method, a laser transfer
method, or an application method such as a spin coating method. For
example, the blue-light-emitting layer according to the preferred
embodiment can be formed by, for example, an evaporation method.
For example, the blue-light-emitting layer is preferably formed by
a vacuum evaporation method at a deposition rate of 0.05 to 2 nm/s
using, for example, 4,4'-N,N'-dicarbazolylbiphenyl (CBP,
blue-light-emitting host material),
9-(4-tert-butylphenyl)-3,6-ditrityl-9H-carbazole (CzC,
blue-light-emitting host material), 1,3-di-9-carbazolylbenzene
(mCP, blue-light-emitting host material), or BD102
(blue-fluorescence-emitting material serving as a
blue-light-emitting dopant, available from Idemitsu Kosan Co.,
Ltd).
[0143] The light-emitting layer according to the present invention
preferably contains a light-emitting material (also referred to as
a "guest material" or "dopant") and a host material. The
light-emitting layer has an average thickness of 1 to 60 nm. The
mixing ratio (by mass) of the host material to the guest material
is not particularly limited and is preferably adjusted to, for
example, 10:1 to 300:1.
[0144] Examples of the light-emitting material according to the
present invention include light-emitting materials capable of
converting singlet excitation energy into light emission and
light-emitting materials capable of converting triplet excitation
energy into light emission. As a light-emitting material contained
in the electroluminescent layer according to the present invention,
one or two or more selected from the group consisting of an
inorganic light-emitting material, an organic low-molecular-weight
fluorescent material, an organic polymer fluorescent material, and
organic phosphorescent materials are preferably contained.
[0145] Examples of the light-emitting material capable of
converting singlet excitation energy into light emission include
the low-molecular-weight fluorescent material that fluoresces and
the organic polymer fluorescent material.
[0146] The low-molecular-weight fluorescent material is preferably
a compound having an anthracene moiety, a tetracene moiety, a
chrysene moiety, a phenanthrene moiety, a pyrene moiety, a perylene
moiety, a stilbene moiety, an acridone moiety, a coumarin moiety, a
phenoxazine moiety, and a phenothiazine moiety. Examples thereof
include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine,
5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine,
N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine,
4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine,
4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine,
N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine,
4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine,
4-[4-(10-phenyl-9-anthryl)phenyl]-4'-(9-phenyl-9H-carbazol-3-yl)triphenyl-
amine, perylene, 2,5,8,11-tetra(tert-butyl)perylene,
N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diam-
ine,
N,N'-bis(3-methyiphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-
-pyrene-1,6-diamine,
N,N'-bis(dibenzofuran-2-yl)-N,N'-diphenylpyrene-1,6-diamine,
N,N'-bis(dibenzothiophen-2-yl)-N,N'-diphenylpyrene-1,6-diamine,
N,N''-(2-tert-butylanthracen-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphe-
nyl-1,4-phenylenediamine],
N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazole-3-amine,
N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,
N',N'-triphenyl-1,4-phenylenediamine, N,
N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraa-
mine, coumarin 30,
N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazole-3-amine,
N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine,
N, N, 9-triphenylanthracene-9-amine, coumarin 6, coumarin 545T,
N,N'-diphenylquinacridon, rubrene,
5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene,
2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)pro-
panedinitrile, 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,
5H-benzo[ij]quinolizin-9-yl)
ethenyl]-4H-pyran-4-ylidene}propanedinitrile,
N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine,
7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluorant-
hene-3,10-diamine,
2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,
5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile,
2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[-
ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile,
2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propane-
dinitrile,
2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro--
1H,5H-benzo[ij]quinolizin-9-yl)
ethenyl]-4H-pyran-4-ylidene}propanedinitrile, and
5,10,15,20-tetraphenylbisbenzo[5,6]indeno[1,2,3-cd:1',2',
3'-lm]perylene.
[0147] Examples of the organic polymer fluorescent material include
compounds represented by formulae (P-1) to (P-4) illustrated
below.
##STR00003##
[0148] The light-emitting material capable of converting triplet
excitation energy into light emission is preferably a
phosphorescent material that phosphoresces. Specifically, the
light-emitting material is preferably a metal complex containing at
least one metal atom selected from the group consisting of iridium,
rhodium, platinum, ruthenium, osmium, scandium, yttrium,
gadolinium, palladium, silver, gold, and aluminum, more preferably
a metal complex containing at least one metal atom selected from
the group consisting of iridium, rhodium, platinum, ruthenium,
osmium, scandium, yttrium, gadolinium, and palladium, even more
preferably a metal complex containing at least one metal atom
selected from the group consisting of iridium, rhodium, platinum,
and ruthenium, particularly preferably an iridium complex or a
platinum complex.
[0149] For example, one or two or more selected from the group
consisting of compounds represented by formulae (I-1) to (I-12)
illustrated below are preferred.
##STR00004## ##STR00005## ##STR00006##
[0150] A compound having a blue emission peak used for the
light-emitting layer according to the present invention is
preferably an iridium metal complex or a platinum metal complex. In
addition to the compounds, examples of the iridium metal complex
include
tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-.-
kappa.N2]phenyl-.kappa.C}iridium(III),
tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III),
tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)-
,
tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III-
),
tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(I-
II),
tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III),
fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III),
tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridiu-
m(III), bis[2-(4',6'-difluorophenyl)pyridinato-N,C2']iridium(III)
tetrakis(1-pyrazolyl)borate,
bis[2-(4',6'-difluorophenyl)pyridinato-N,C2']iridium(III)
picolinate,
bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C2'}iridium(III)
picolinate, and
bis[2-(4',6'-difluorophenyl)pyridinato-N,C2']iridium(III)
acetylacetonate.
[0151] Compounds illustrated below may also be appropriately used
as a compound having a blue emission peak for use in the
light-emitting layer according to the present invention.
##STR00007##
[0152] As a compound having a green or yellow emission peak used
for the light-emitting layer according to the present invention, a
known compound may be used. Examples thereof include
tris(4-methyl-6-phenylpyrimidinato)iridium(III),
tris(4-t-butyl-6-phenylpyrimidinato)iridium(III),
(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III),
(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III),
(acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III),
(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iri-
dium(III),
(acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-p-
yrimidinyl-.kappa.N3]phenyl-KC}iridium(III),
(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III),
(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III),
(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)-
, tris(2-phenylpyridinato-N,C2')iridium(III,
bis(2-phenylpyridinato-N,C2')iridium(III) acetylacetonate,
bis(benzo[h]quinolinato)iridium(III) acetylacetonate,
tris(benzo[h]quinolinato)iridium(III),
tris(2-phenylquinolinato-N,C2')iridium(III),
bis(2-phenylquinolinato-N,C2')iridium(III) acetylacetonate,
bis(2,4-diphenyl-1,3-oxazolato-N,C2')iridium(III) acetylacetonate,
bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C2'}iridium(III)
acetylacetonate, bis(2-phenylbenzothiazolato-N,C2')iridium(III)
acetylacetonate and tris(acetylacetonato)
(monophenanthroline)terbium(III).
[0153] As a compound having a yellow or red emission peak used for
the light-emitting layer according to the present invention, a
known compound may be used. Examples thereof include
(diisobutylyl)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III),
bis[4,6-bis(3-methylphenyl)pyrimidinato]
(dipivaloylmethanato)iridium(III),
bis[4,6-di(naphthalen-1-yl)pyrimidinato]
(dipivaloylmethanato)iridium(III),
(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III),
bis(2,3,5-triphenylpyrazinato) (dipivaloylmethanato)iridium(III),
(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III),
tris(1-phenylisoquinolinato-N,C2')iridium(III),
bis(1-phenylisoquinolinato-N,C2')iridium(III) acetylacetonate,
2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II),
tris(1,3-diphenyl-1,3-propanedionato)
(monophenanthroline)europium(III), and
tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato]
(monophenanthroline)europium(III).
[0154] As a host material for the light-emitting layer according to
the present invention, a known material may be used. In this case,
one or two or more compounds each having a larger energy gap than
the light-emitting material described above are preferably selected
and used as the host material. In the case where the light-emitting
material is a phosphorescent material, a compound having higher
triplet excitation energy (difference in energy between a ground
state and a triplet excited state) than the light-emitting material
is preferably selected as the host material.
[0155] Examples of the host material include
tris(8-quinolinolato)aluminum(III),
tris(4-methyl-8-quinolinolato)aluminum(III),
bis(10-hydroxybenzo[h]quinolinato)beryllium(II),
bis(2-methyl-8-quinolinolato) (4-phenylphenolato)aluminum(III),
bis(8-quinolinolato)zinc(II),
bis[2-(2-benzoxazolyl)phenolato]zinc(II),
bis[2-(2-benzothiazolyl)phenolato]zinc(II),
2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole,
1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene,
3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole,
2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole),
bathophenanthroline, bathocuproine,
9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole,
9,10-diphenylanthracene,
N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine,
4-(10-phenyl-9-anthryl)triphenylamine,
N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazole-3-a-
mine, 6,12-dimethoxy-5,11-diphenylchrysene,
9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole,
3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole,
9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole,
7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole,
6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan,
9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene,
9,10-bis(3,5-diphenylphenyl)anthracene,
9,10-di(2-naphthyl)anthracene,
2-tert-butyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl,
9,9'-(stilben-3,3'-diyl)diphenanthrene,
9,9'-(stilben-4,4'-diyl)diphenanthrene,
1,3,5-tri(1-pyrenyl)benzene, 5,12-diphenyltetracene and
5,12-bis(biphenyl-2-yl)tetracene. These host materials for the
light-emitting layer according to the present invention may be used
alone or in combination of two or more of the compounds.
"Hole Injection Layer"
[0156] As a material used for the hole injection layer according to
the present invention, a substance that prevents leakage current
and improves the hole injection rate may be used. Examples thereof
include transition metal oxides, phthalocyanine derivatives,
aromatic amines, and conductive polymer compounds.
[0157] Examples of the transition metal oxides include molybdenum
oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and
manganese oxide. Examples of the phthalocyanine derivatives include
phthalocyanine and metal phthalocyanine such as copper
phthalocyanine. Examples of the conductive polymer compounds
include polythiophene, polyaniline, polypyrrole, poly(phenylene
vinylene), poly(thienylene vinylene, polyquinone, polyquinoxaline,
and poly(ethylene dioxythiophene)/poly(styrene sulfonic acid).
Examples of the aromatic amines include benzidine derivatives,
phenylenediamine derivatives, and triarylamine derivatives.
[0158] As with the electron injection layer, a composite material
containing a mixture of an organic compound (acceptor) and an
electron-donating material (donor) may be used for the hole
injection layer according to the present invention. Examples of the
electron-donating material (donor) include quinodimethan
derivatives, chloranil derivatives, and hexaazatriphenylene
derivatives. Specific examples thereof include
7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethan, chloranil, and
2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene.
Furthermore, oxides of group 4 to 8 metals are exemplified as the
electron-donating material (donor). Examples thereof include
vanadium oxide, niobium oxide, tantalum oxide, chromium oxide,
molybdenum oxide, tungsten oxide, manganese oxide, and rhenium
oxide.
"Hole Transport Layer"
[0159] As a material used for the hole transport layer according to
the present invention, a material whose hole transport ability is
higher than its electron transport ability is preferably used.
Examples thereof include aromatic amines, carbazole derivatives,
aromatic hydrocarbons, and stilbene derivatives. For example,
.pi.-electron-rich heteroaromatic compounds and aromatic amines may
be preferably used.
[0160] Examples of the material used for the hole transport layer
according to the present invention include
N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine,
4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl,
N,N'-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N'-diphenyl-(1,1'-biphenyl-
)-4,4'-diamine,
1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene,
3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole,
3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole,
3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole,
3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole,
3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole,
3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole,
4,4'-di(N-carbazolyl)biphenyl,
1,3,5-tris[4-(N-carbazolyl)phenyl]benzene,
9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole,
1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene,
2-tert-butyl-9,10-di(2-naphthyl)anthracene,
2-tert-butyl-9,10-di(1-naphthyl)anthracene,
9,10-bis(3,5-diphenylphenyl)anthracene,
2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene,
9,10-di(2-naphthyl) anthracene, 9,10-diphenylanthracene,
2-tert-butylanthracene, 9,10-bis(4-methyl-1-naphthyl)anthracene,
2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene,
9,10-bis[2-(1-naphthyl)phenyl]anthracene,
2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene,
2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9'-bianthryl,
10,10'-diphenyl-9,9'-bianthryl,
10,10'-bis(2-phenylphenyl)-9,9'-bianthryl,
10,10'-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9'-bianthryl,
anthracene, tetracene, rubrene, perylene,
2,5,8,11-tetra(tert-butyl)perylene,
4,4'-bis(2,2-diphenylvinyl)biphenyl,
9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene,
poly(N-vinylcarbazole), poly(4-vinyltriphenylamine),
poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)met-
hacrylamide],
poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine],
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl,
N,N'-bis(3-methyiphenyl)-tris(carbazol-9-yl)triphenylamine,
4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine,
4,4',4''-tris(N,N-diphenylamino)triphenylamine,
4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine,
4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl,
4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine,
4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine,
N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dim-
ethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine,
N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine,
2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene,
4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine,
4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine,
4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine,
4,4'-di(1-naphthyl)-4'''-(9-phenyl-9H-carbazol-3-yl)triphenylamine,
4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine,
N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine,
N,N',N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-tria-
mine,
N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-
e-3-amine,
N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]--
9,9-dimethyl-9H-fluorene-2-amine,
9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluorene-2-a-
mine,
N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-
e-2-amine,
2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluoren- e,
2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9'-bifluorene,
N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline,
N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7--
diamine, 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole,
3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole,
3,3'-bis(9-phenyl-9H-carbazole), 1,3-bis(N-carbazolyl)benzene,
3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole,
4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran,
4,4',4'''-(benzene-1,3,5-triyl)tri(dibenzofran),
1,3,5-tri(dibenzothiophen-4-yl)-benzene,
2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene,
4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene,
and 4-[3-(triphenylen-2-yl)phenyl]dibenzothiophene. A functional
layer such as an electron-blocking layer that can control electron
transfer may be disposed between the hole transport layer and the
light-emitting layer.
[0161] The layer containing a substance having high hole transport
ability may be formed of a single layer or a stack of two or more
layers containing the foregoing compound.
[0162] In the electroluminescent layer according to the present
invention, it is preferable that the HOMO level of the compound of
the hole transport layer be higher than the HOMO level of the
compound of the electron transport layer and that the LUMO level of
the compound of the hole transport layer be higher than the LUMO
level of the compound of the electron transport layer. Thereby, an
excited complex seems to be effectively formed.
[0163] As a light-emitting material for the light-emitting layer
according to the present invention, a thermally activated delayed
fluorescent (TADF) material may be used in place of the foregoing
light-emitting material. The thermally activated delayed
fluorescent material has a small difference between the singlet
excitation energy level and the triplet excitation energy level and
serves to convert energy through reverse intersystem crossing from
the triplet excited state to the single excited state.
[0164] Examples of the thermally activated delayed fluorescent
material include fullerenes and their derivatives, acridine
derivatives (proflavine), porphyrin containing a metal containing
at least one selected from the group consisting of magnesium, zinc,
cadmium, tin, platinum, indium, and palladium, and heterocyclic
thermally activated delayed fluorescent materials.
[0165] Examples of the porphyrin include protoporphyrin-tin
fluoride complex (SnF.sub.2 (Proto IX)), mesoporphyrin-tin fluoride
complex (SnF.sub.2 (Meso IX)), hematoporphyrin-tin fluoride complex
(SnF.sub.2 (Hemato IX)), coproporphyrin tetramethyl ester-tin
fluoride complex (SnF.sub.2 (Copro III-4Me)),
octaethylporphyrin-tin fluoride complex (SnF.sub.2 (OEP)),
etioporphyrin-tin fluoride complex (SnF.sub.2 (Etio I)), and
octaethylporphyrin-platinum chloride complex (PtCl.sub.2 OEP).
[0166] Examples of the heterocyclic thermally activated delayed
fluorescent material include compounds represented by formulae
(II-1) to (II-7) illustrated below.
##STR00008## ##STR00009##
[0167] Other examples of the heterocyclic thermally activated
delayed fluorescent material include
2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-tri-
azine,
2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-di-
phenyl-1,3,5-triazine,
2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine,
3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-tria-
zole, 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one,
bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone, and
10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracen]-10'-one.
[0168] In the thermally activated delayed fluorescent material, a
single type of compound may be used alone, or two or more types of
compounds may be used in combination.
[0169] The electroluminescent layer (the light-emitting layer, the
hole injection layer, the hole transport layer, the electron
transport layer, and the electron injection layer) according to the
present invention may be formed by a known production method.
Examples thereof include an evaporation method, a vacuum deposition
method, an inkjet method, an application method, and gravure
printing.
[0170] A second aspect of the present invention is directed to
providing an image display apparatus including a light-emitting
device and a transistor layer.
[0171] Specifically, the image display apparatus according to the
present invention includes a pair of electrodes including a first
electrode and a second electrode disposed opposite each other, an
electroluminescent layer disposed between the first electrode and
the second electrode, a light conversion layer including multiple
pixels and converting light that is emitted from the
electroluminescent layer and that has a blue emission spectrum into
light having a different wavelength, and a transistor layer
electrically connected to the first electrode or the second
electrode, in which the light conversion layer includes pixels of
three primary colors of red (R), green (G), and blue (B) and
contains a light-emitting nanocrystal having an emission spectrum
in any of red (R), green (G), and blue (B) when the light from the
electroluminescent layer is incident on at least one of the three
primary colors.
[0172] The image display apparatus according to the present
invention includes multiple pixels arranged in a grid. The pixels
include the light-emitting device and the transistor layer
including a pixel circuit that drives the light-emitting device.
Light emission is controlled by signals from a scan line driver
circuit and a signal line driver circuit. The transistor layer
according to the present invention will be described below with
reference to FIGS. 8 and 9.
[0173] FIG. 8 is a schematic circuit diagram illustrating a
transistor layer according to the present invention and illustrates
an example of the circuit configuration of pixels in the image
display apparatus according to the present invention. In FIGS. 8
and 9, R, G, and B regions each correspond to one pixel. The
transistor layer includes at least two of a switching transistor
708 and a driver transistor 702 in each pixel. In the transistor
layer, a control circuit controls the scan line driver circuit, the
signal line driver circuit, and an image display portion (not
illustrated) and outputs a signal voltage based on an image signal
input from the outside to the signal line driver circuit. The image
display portion (not illustrated) includes the multiple pixels (R,
G, and B) arranged in a grid. An image is displayed in the image
display portion on the basis of the image signal. The scan line
driver circuit outputs a scan signal to scan lines 707 to control
the ON/OFF of the conduction of the switching transistors 708 in
the pixels. The signal line driver circuit is connected to signal
lines 706 and has the function of outputting a signal voltage based
on an image signal to the pixels.
[0174] As illustrated in FIGS. 8 and 9, the signal lines 706
connect the signal line driver circuit to the respective pixels and
have the function of supplying a signal voltage based on an image
signal to each pixel. The scan lines 707 connect the scan line
driver circuit to the light-emitting pixels and have the function
of supplying the timing of writing the signal voltage.
[0175] As illustrated in FIG. 9, each pixel includes the driver
transistor 702, the switching transistor 708, a capacitor 701, the
light-emitting device 100, the signal line 706, the scan line 707,
a power supply line 703, and a common electrode 705. The driver
transistor 702 is a driver element in which a gate electrode is
connected to one electrode of the capacitor 701, a source electrode
is connected to an anode electrode (anode, first electrode) of the
light-emitting device 100, and a drain electrode is connected to
the other electrode of the capacitor 701 and to the power supply
line 703. The driver transistor 702 converts a voltage
corresponding to a signal voltage applied between the gate
electrode and the source electrode into a drain current
corresponding to the signal voltage. The drain current is supplied
to the light-emitting device 100 as a signal current. The driver
transistor 702 is preferably formed of a known thin-film transistor
or the like. The power supply line 703 is a line to apply a voltage
to the drain electrode of the driver transistor 702. The common
electrode 705 is an electrode to apply a voltage to the cathode
electrode of the light-emitting device 100.
[0176] The switching transistor 708 is a switching element in which
a gate electrode is connected to the scan line 707, one of a source
electrode and a drain electrode is connected to the gate electrode
of the driver transistor 702, and the remaining one of the source
electrode and the drain electrode is connected to the signal line
706. The capacitor 701 is a capacitive element in which one
electrode is connected to the gate electrode of the driver
transistor 702 and the other electrode is connected to the drain
electrode of the driver transistor 702.
[0177] The light-emitting device 100 is a light-emitting device in
which a cathode electrode (cathode, second electrode) is connected
to the common electrode 705, the anode electrode (anode, first
electrode) is connected to the source electrode of the driver
transistor 702, and light is emitted in accordance with a current
supplied from the driver transistor 702.
[0178] As illustrated in FIGS. 1 to 7 and described above, the
light-emitting device 100 according to the present invention is a
top-emission light-emitting device in which light emitted by the
recombination of holes injected from the first electrode 2 with
electrons injected from the second electrode 8 is displayed from
the second electrode 8 side. Thus, in an image display apparatus
101 according to the present invention, the transistor layer
including the transistor that drives the pixel circuit is
preferably disposed between the first electrode 2 and the substrate
1 with reference to, for example, FIG. 1. In this case, the
transistor layer is preferably electrically connected to the first
electrode 2.
[0179] In the case where the light-emitting device 100 or the image
display apparatus according to the present invention is of a
top-emission type, the substrate 11 and an overcoat layer is
preferably transparent. A polarizing layer may be disposed on the
substrate 11 to block light coming from the outside, as needed.
[0180] The light-emitting device according to the present invention
may be of a bottom-emission type in which light is taken from the
first electrode 2 side.
[0181] An embodiment of the bottom-emission image display apparatus
will be described below with reference to FIG. 10. FIG. 10 is a
schematic cross-sectional view illustrating the image display
apparatus 101. The image display apparatus 101 of the present
invention includes the light-emitting device 100 and a transistor
layer 20. The light-emitting device 100 includes the first
electrode 2 and the second electrode 8 as a pair of opposite
electrodes, the electroluminescent layer 12 disposed between the
electrodes, and the light conversion layer 9 disposed on the other
surface of the first electrode 2. The transistor layer 20 including
a transistor that drives a pixel circuit is disposed between the
substrate 1 and the light conversion layer 9.
[0182] The electroluminescent layer 12 only needs to include at
least the light-emitting layer 5. The electroluminescent layer 12
according to the present invention preferably includes the hole
injection layer 3, the hole transport layer 4, the light-emitting
layer 5, the electron transport layer 6, and the electron injection
layer 7. Similarly, in the bottom-emission light-emitting device
and the bottom-emission image display apparatus, an
electron-blocking layer may be disposed between the light-emitting
layer 5 and the electron transport layer 6, as needed, and a
hole-blocking layer may be disposed between the hole transport
layer 4 and the light-emitting layer 5, as needed. As the
light-emitting layer 5, a light-emitting layer that emits blue
light is preferred.
[0183] In the light-emitting device 100 of the image display
apparatus, the electroluminescent layer 12 includes the hole
injection layer 3 in contact with the first electrode 2 and has a
structure in which the hole transport layer 4, the light-emitting
layer 5, and the electron transport layer 6 are stacked in this
order.
[0184] In an embodiment of the present invention, in the following
description, for convenience, the first electrode 2 serves as an
anode, and the second electrode 8 serves as a cathode. However, the
structure of the light-emitting device 100 is not limited thereto.
The first electrode 2 serving as a cathode and the second electrode
8 serving as an anode may be used, and the layers between these
electrodes may be stacked in reverse order. In other words, the
hole injection layer, the hole transport layer, the light-emitting
layer, the electron transport layer, and the electron injection
layer may be stacked in this order from the second electrode 8
adjacent to the anode.
[0185] In the case of the bottom-emission type, because light
emerges from the first electrode 2 side, the second electrode 8 is
preferably a light-reflecting electrode having the function of
reflecting light (for example, Al or ITO/Ag/ITO). In the case of
the top-emission type, the second electrode 8 is preferably a
transparent electrode.
[0186] In the image display apparatus 101 illustrated in FIG. 10,
the application of a voltage between the first electrode 2 and the
second electrode 8 permits electrons to be injected from the second
electrode 8 of the cathode into the electroluminescent layer 12 and
permits holes to be injected from the first electrode 2 of the
anode into the electroluminescent layer 12, so that a current
flows. The electrons and the holes injected are recombined to form
excitons. As a result, the light-emitting material contained in the
light-emitting layer 5 is in an excited state to emit light from
the light-emitting material. Then light emitted from the
light-emitting layer 5 is incident on a surface of the light
conversion layer 9 through the hole transport layer 4, the hole
injection layer 3, the first electrode (first transparent
electrode) 2, and the transistor layer 20. The light incident on
the light conversion layer 9 is absorbed by the light-emitting
nanocrystals and converted into light having an emission spectrum
in any of red (R), green (G), and blue (B), so that any of red (R),
green (G), and blue (B) can be displayed. Light that is a component
of the light emitted from the light-emitting layer 5 and that
travels toward the second electrode 8 side is reflected from the
second electrode 8 (reflecting electrode), travels toward the first
electrode 2 side, and is converted by the light conversion layer 9
into an emission spectrum, so that any of red (R), green (G), and
blue (B) can be displayed.
[0187] The image display apparatus according to the present
invention includes the transistor layer electrically connected to
the first electrode or the second electrode. Light emitted from the
electroluminescent layer is displayed through the light conversion
layer and the transistor layer.
[0188] The top-emission image display apparatus preferably has a
structure in which the substrate 1, the transistor layer 20, the
first electrode 2, the hole injection layer 3, the hole transport
layer 4, the light-emitting layer 5, the electron transport layer
6, the electron injection layer 7, the second electrode 8, the
light conversion layer 9, and the substrate 11 are stacked in this
order. Thus, light emitted from the electroluminescent layer 12 is
displayed without passing through the transistor layer 20. As the
light-emitting layer 5, a light-emitting layer that emits blue
light is preferred.
[0189] The polarizing layer according to the present invention is
not particularly limited. A known polarizer (polarizing layer) may
be used. Examples thereof include dichroic organic dye polarizers,
polarizing layers formed by coating, wire-grid polarizers, and
cholesteric liquid crystal polarizers. For example, preferably, the
wire-grid polarizer is formed on a first substrate, a second
substrate, or a color filter by one selected from nanoimprinting
methods, block copolymer methods, E-beam lithography methods, and
glancing angle deposition methods.
EXAMPLES
[0190] While the present invention will be described below in more
detail by examples, the present invention is not limited
thereto.
(1) Production of Image Display Apparatus Panel (Production of
Light Conversion Layer or Color Filter)
(A) Production of Red-Light-Emitting-Nanocrystal-Containing
Composition, Green-Light-Emitting-Nanocrystal-Containing
Composition, and Blue (-Light-Emitting-Nanocrystal-Containing)
Composition
[Light Diffusing Particle Dispersion]
[0191] In a container filled with nitrogen gas, 2.4 g of titanium
oxide (trade name: MPT141, available from Ishihara Sangyo Kaisha,
Ltd., average particle size (volume average size): 100 nm), 0.4 g
of DISPERBYK-2164 (trade name of BYK, "DISPERBYK" is a registered
trademark) as a polymer dispersant, and 1,4-butanediol diacetate
were mixed. Then zirconia beads (diameter: 1.25 mm) were added to
the resulting mixture. The mixture was shaken with a paint
conditioner to perform dispersion treatment of the mixture. Removal
of the zirconia beads with a polyester mesh filter resulted in a
light diffusing particle dispersion 1 (non-volatile content: 44% by
mass).
[Red-Light-Emitting-Nanocrystal-Containing Composition 1]
[0192] First, 30 parts by mass of red-light-emitting nanocrystals
(CdSe/ZnS oleylamine ligand, emission peak: 620 nm), 30 parts by
mass of dipentaerythritol hexaacrylate (KAYARAD (trade name) DPHA,
available from Nippon Kayaku Co., Ltd.), 5 parts by mass of a
polymerization initiator (Irgacure-907 (tradename), available from
BASF), and 30 parts by mass of a polyester acrylate resin (Aronix
(trade name) M7100, available from Toagosei Co., Ltd.) were mixed
and diluted with propylene glycol monomethyl ether acetate so as to
have a solid content of 20% by mass. The mixture was stirred with a
dispersion stirrer and filtered with a filter having a pore size of
1.0 .mu.m to provide a red-light-emitting-nanocrystal-containing
composition 1.
[Red-Light-Emitting-Nanocrystal-Containing Composition 2]
[0193] A red-light-emitting-nanocrystal-containing composition 2
was prepared in the same way as above, except that
red-light-emitting nanocrystals (InP/ZnS oleylamine ligand,
emission peak: 530 nm) was used in place of the red-light-emitting
nanocrystals CdSe/ZnS in the
red-light-emitting-nanocrystal-containing composition.
[Red-Light-Emitting Nanocrystal-Containing Composition 3]
[0194] Into a reaction flask, 5 g of trioctylphosphine oxide
(TOPO), 1.46 g (5 mmol) of indium acetate, and 3.16 g (15.8 mmol)
of lauric acid were charged, thereby preparing a mixture. The
mixture was heated at 160.degree. C. for 40 minutes in a nitrogen
(N.sub.2) environment and then heated under vacuum at 250.degree.
C. for 20 minutes. The reaction temperature (the temperature of the
mixture) was increased to 300.degree. C. in the nitrogen (N.sub.2)
environment. At this temperature, a mixture of 3 g of 1-octadecene
(ODE) and 0.25 g (1 mmol) of tris(trimethylsilyl)phosphine was
rapidly introduced into the reaction flask. The reaction
temperature was maintained at 260.degree. C. After 5 minutes, a
heater was removed to stop the reaction. The resulting reaction
solution was cooled to room temperature. Then 8 ml of toluene and
20 ml of ethanol were added to the reaction solution in a glove
box. Subsequently, centrifugal separation was performed to
precipitate InP nanocrystalline particles. The decantation of the
supernatant fluid resulted in the InP nanocrystal particles. The
resulting InP nanocrystalline particles were dispersed in hexane,
thereby preparing a dispersion (hexane dispersion) containing 5% by
mass InP nanocrystalline particles.
[0195] To a reaction flask, 2.5 g of the hexane dispersion of InP
nanocrystalline particles (InP cores) was added. Then 0.7 g of
oleic acid was added to the reaction flask at room temperature. The
temperature thereof was increased to 80.degree. C. and maintained
for 2 hours. Subsequently, 1 ml of 1-octadecene (ODE) containing 14
mg of diethylzinc, 8 mg of bis(trimethylsilyl)selenide, and 7 mg of
hexamethyldisilathiane dissolved therein (ZnSeS precursor solution)
was added dropwise to the reaction mixture. The temperature of the
mixture was increased to 200.degree. C. and maintained for 10
minutes, thereby forming ZnSeS shells having a thickness of 0.5
monolayer.
[0196] The temperature thereof was increased to 140.degree. C. and
maintained for 30 minutes. A ZnS precursor solution prepared by
dissolving 69 mg of diethylzinc and 66 mg of hexamethyldisilathiane
in 2 ml of ODE was added dropwise to the reaction mixture. The
temperature thereof was increased to 200.degree. C. and maintained
for 30 minutes, thereby forming ZnS shells having a thickness of 2
monolayers. After 10 minutes of the dropwise addition of the ZnS
precursor solution, a heater was removed to stop the reaction. The
reaction mixture was cooled to room temperature. The resulting
white precipitate was removed by centrifugal separation, thereby
providing a transparent nanocrystal dispersion (ODE dispersion of
InP/ZnSeS/ZnS nanocrystalline particles) containing
red-light-emitting InP/ZnSeS/ZnS nanocrystalline particles
dispersed therein.
[0197] A ligand represented by formula (1A) below was obtained from
JEFFAMINE M-1000 (available from Huntsman Corp.) and succinic
anhydride (available from Sigma-Aldrich) in a molar amount equal to
that of JEFAMINE M-1000 under a stream of nitrogen gas.
##STR00010##
[0198] Then 30 mg of the organic ligand represented by formula (1A)
was added to the 1 ml of ODE dispersion of the InP/ZnSeS/ZnS
nanocrystalline particles. The mixture was heated at 90.degree. C.
for 5 hours to exchange the ligand. The nanocrystalline particles
aggregated as the ligand exchange proceeded. After the completion
of the ligand exchange, the decantation of the supernatant fluid
resulted in nanocrystalline particles. To the nanocrystalline
particles, 3 ml of ethanol was added. The mixture was subjected to
ultrasonic treatment to perform redispersion. Then 10 ml of
n-hexane was added to 3 mL of the ethanol dispersion of the
nanocrystalline particles. Subsequently, centrifugal separation was
performed to precipitate nanocrystalline particles. The decantation
of the supernatant fluid and evaporation were performed under
vacuum to provide nanocrystalline particles (InP/ZnSeS/ZnS
nanocrystalline particles modified with the organic ligand). The
organic ligand content was 30% by mass based on the total amount of
the nanocrystalline particles modified with the organic ligand.
[0199] The nanocrystalline particles (the InP/ZnSeS/ZnS
nanocrystalline particles modified with the organic ligand) were
dispersed in EOEOA in such a manner that the resulting dispersion
had a nanocrystalline particle content of 34.5% by mass, thereby
providing a dispersion 1 of red-light-emitting nanocrystals. The
dispersion had an EOEOA content of 65.5% by mass.
[0200] Next, 0.28 g of Finedic A-254 (available from DIC
Corporation, "Finedic" is a registered trademark) serving as a
thermosetting resin, 0.09 g of 1-methylcyclohexane-4,5-dicarboxylic
anhydride (available from Tokyo Chemical Industry Co., Ltd.), and
0.004 g of dimethylbenzylamine were dissolved in 1,4-butanediol
diacetate to prepare a thermosetting resin solution 1 (non-volatile
content: 30% by mass).
[0201] After 2.25 g of the dispersion 1 containing light-emitting
nanocrystals, 0.75 g of the light diffusing particle dispersion 1,
and 1.25 g of the thermosetting resin solution 1 were mixed, the
mixture was filtered with a filter having a pore size of 5 .mu.m,
thereby providing a red-light-emitting-nanocrystal-containing
composition 3.
[Green-Light-Emitting-Nanocrystal-Containing Composition 1]
[0202] A green-light-emitting-nanocrystal-containing composition 1
was prepared in the same way as above, except that
green-light-emitting nanocrystals (CdSe/ZnS oleylamine ligand,
emission peak: 530 nm) was used in place of the red-light-emitting
nanocrystals CdSe/ZnS in the
red-light-emitting-nanocrystal-containing composition.
[Green-Light-Emitting-Nanocrystal-Containing Composition 2]
[0203] A green-light-emitting-nanocrystal-containing composition 2
was prepared in the same way as above, except that
green-light-emitting nanocrystals (InP/ZnS oleylamine ligand,
emission peak: 620 nm) was used in place of the red-light-emitting
nanocrystals CdSe/ZnS in the
red-light-emitting-nanocrystal-containing composition.
[Green-Light-Emitting-Nanocrystal-Containing Composition 3]
[0204] First, 5 g of trioctylphosphine oxide (TOPO), 1.46 g (5
mmol) of indium acetate, and 3.16 g (15.8 mmol) of lauric acid were
added to a reaction flask to prepare a mixture. The mixture was
heated at 160.degree. C. for 40 minutes in a nitrogen (N.sub.2)
environment and then heated under vacuum at 250.degree. C. for 20
minutes. The reaction temperature (the temperature of the mixture)
was increased to 300.degree. C. in the nitrogen (N.sub.2)
environment. At this temperature, a mixture of 3 g of 1-octadecene
(ODE) and 0.25 g (1 mmol) of tris(trimethylsilyl)phosphine was
rapidly introduced into the reaction flask. The reaction
temperature was maintained at 260.degree. C. After 5 minutes, a
heater was removed to stop the reaction. The resulting reaction
solution was cooled to room temperature. Then 8 ml of toluene and
20 ml of ethanol were added to the reaction solution in a glove
box. Subsequently, centrifugal separation was performed to
precipitate InP nanocrystalline particles (InP cores). The
decantation of the supernatant fluid resulted in the InP
nanocrystal particles (InP cores). The resulting InP
nanocrystalline particles (InP cores) were dispersed in hexane,
thereby preparing a dispersion (hexane dispersion) containing 5% by
mass InP nanocrystalline particles (InP cores).
[0205] To a reaction flask, 2.5 g of the hexane dispersion of InP
nanocrystalline particles (InP cores) was added. Then 0.7 g of
oleic acid was added to the reaction flask at room temperature. The
temperature thereof was increased to 80.degree. C. Subsequently, 1
ml of ODE containing 14 mg of diethylzinc, 8 mg of
bis(trimethylsilyl)selenide, and 7 mg of hexamethyldisilathiane
dissolved therein (ZnSeS precursor solution) was added dropwise to
the reaction mixture, thereby forming ZnSeS shells having a
thickness of 0.5 monolayer.
[0206] After dropwise addition of the ZnSeS precursor solution, the
reaction temperature was maintained at 80.degree. C. for 10
minutes. The temperature was increased to 140.degree. C. and
maintained for 30 minutes. A ZnS precursor solution prepared by
dissolving 69 mg of diethylzinc and 66 mg of hexamethyldisilathiane
in 2 ml of ODE was added dropwise to the reaction mixture, thereby
forming ZnS shells having a thickness of 2 monolayers. After 10
minutes of the dropwise addition of ZnS precursor solution, a
heater was removed to stop the reaction. The reaction mixture was
cooled to room temperature. The resulting white precipitate was
removed by centrifugal separation, thereby providing a transparent
nanocrystalline particle dispersion (ODE dispersion) containing
green-light-emitting InP/ZnSeS/ZnS nanocrystalline particles
dispersed therein.
[0207] Then 30 mg of the organic ligand was added to the 1 ml of
ODE dispersion of the InP/ZnSeS/ZnS nanocrystalline particles. The
mixture was heated at 90.degree. C. for 5 hours to exchange the
ligand. The nanocrystalline particles aggregated as the ligand
exchange proceeded. After the completion of the ligand exchange,
the supernatant fluid was decanted. To the resulting
nanocrystalline particles, 3 ml of ethanol was added. The mixture
was subjected to ultrasonic treatment to perform redispersion. Then
10 ml of n-hexane was added to 3 mL of the ethanol dispersion of
the nanocrystalline particles. Subsequently, centrifugal separation
was performed to precipitate nanocrystalline particles. The
decantation of the supernatant fluid and evaporation were performed
under vacuum to provide nanocrystalline particles (InP/ZnSeS/ZnS
nanocrystalline particles modified with the organic ligand). The
organic ligand content was 35% by mass based on the total amount of
the nanocrystalline particles modified with the organic ligand. The
nanocrystalline particles (the InP/ZnSeS/ZnS nanocrystalline
particles modified with the organic ligand) were dispersed in EOEOA
in such a manner that the resulting dispersion had a
nanocrystalline particle content of 30.0% by mass, thereby
providing a dispersion 1 of green-light-emitting nanocrystalline
particles. The dispersion had an EOEOA content of 70.0% by
mass.
[0208] A green-light-emitting-nanocrystal-containing composition 3
was prepared as in the red-light-emitting-nanocrystal-containing
composition 3, except that the dispersion 1 of green-light-emitting
nanocrystalline particles was used in place of the dispersion 1 of
the red-light-emitting nanocrystalline particles.
[Blue-Coloring Composition 1]
[0209] A blue-coloring composition 1 was prepared as described
below. Propylene glycol monomethyl ether acetate, DISPERBYK
LPN21116 (available from BYK Chemie), and zirconia beads "ER-120S"
having a diameter of 0.3 to 0.4 mm, available from Saint-Gobain,
were mixed and dispersed with a paint conditioner (available from
Toyo Seiki Seisaku-sho, Ltd.) for 4 hours. The mixture was filtered
with a filter having a pore size of 1 .mu.m to prepare a
dispersion. Then 75 parts by mass of the dispersion, 5.5 parts by
mass of a polyester acrylate resin (Aronix (trade name) M7100,
available from Toagosei Co., Ltd.), 5 parts by mass of
dipentaerythritol hexaacrylate (KAYARAD (trade name) DPHA,
available from Nippon Kayaku Co., Ltd.), 1 part by mass of
benzophenone (Kayacure (trade name) BP-100, available from Nippon
Kayaku Co., Ltd.), and 13.5 parts by mass of UCAR Ester EEP were
stirred with a dispersion stirrer and filtered with a filter having
a pore size of 1.0 .mu.m to provide a blue-coloring composition
1.
[Blue-Coloring Composition 2]
[0210] A blue-coloring composition 2 was prepared as described
below. A blue dye 1 (C.I. Solvent Blue 7) was placed in a plastic
container. Propylene glycol monomethyl ether acetate, DISPERBYK
LPN21116 (available from BYK Chemie), and zirconia beads "ER-120S"
having a diameter of 0.3 to 0.4 mm, available from Saint-Gobain,
were added thereto. The mixture was dispersed with a paint
conditioner (available from Toyo Seiki Seisaku-sho, Ltd.) for 4
hours and then filtered with a filter having a pore size of 1 .mu.m
to prepare the dispersion.
[Preparation of Light-Scattering Composition ScB]
[0211] A light-scattering ink composition ScB was prepared as in
the red-light-emitting nanocrystal-containing composition 3, except
that 1,4-butanediol diacetate was used in place of the dispersion 1
of the red-light-emitting nanocrystals (containing the InP/ZnS
core-shell nanocrystals (that emits red light)).
(B) Production of Light Conversion Layer
(B-1) Photolithography Method
[0212] A red-light-emitting-nanocrystal-containing composition was
applied in a thickness of 2 .mu.m by spin coating to a glass
substrate on which a black matrix and TFTs had been formed in
advance. After drying at 70.degree. C. for 20 minutes, the
resulting film was subjected to striped-pattern exposure using
ultraviolet radiation with an exposure machine including an
ultra-high pressure mercury lamp through a photomask. The film was
subjected to spray development with an alkaline developer for 90
seconds, washed with ion-exchanged water, and dried in air.
Additionally, post baking was performed in a clean oven at
180.degree. C. for 30 minutes, thereby forming red pixels, which
were a stripe-shaped coloring layer, on the transparent
substrate.
[0213] A green-light-emitting-nanocrystal-containing composition
was also applied in a thickness of 2 .mu.m by spin coating and
dried. A strip-shaped coloring layer was exposed and developed at a
position shifted from the red pixels with an exposure machine,
thereby forming green pixels adjacent to the red pixels.
[0214] A glass substrate including a light conversion layer 1 or 3
disposed on a surface thereof and the TFTs stacked thereon, the
light conversion layer including stripe-shaped pixels of three
colors of red, green, and blue, was produced so as to have a
structure described in Table 1 with the
light-emitting-nanocrystal-containing composition for each color
and the coloring composition.
[0215] The blue-coloring composition 2 was applied to the entire
surface of the substrate 1 and irradiated with ultraviolet
radiation to produce a glass substrate including a light conversion
layer 2 on a surface thereof and the TFTs stacked thereon, the
light conversion layer including a blue layer disposed on the
entire surface of the stripe-shaped pixels of three colors of red,
green, and blue.
TABLE-US-00001 TABLE 1 Light conversion Light conversion Light
conversion layer 1 layer 2 layer 3 R pixel portion red-light-
red-light- red-light- emitting- emitting- emitting- nanocrystal-
nanocrystal- nanocrystal- containing containing containing
composition 1 composition 1 composition 2 G pixel portion
green-light- green-light- green-light- emitting- emitting-
emitting- nanocrystal- nanocrystal- nanocrystal- containing
containing containing composition 1 composition 1 composition 2 B
pixel portion blue-coloring blue-coloring blue-coloring composition
1 composition 1 composition 1 (without (without (without
blue-light- blue-light- blue-light- emitting emitting emitting
nanocrystal) nanocrystal) nanocrystal) Blue pixel on no
blue-coloring entire pixel composition 2
(B-2) Inkjet Method
[0216] Metallic chromium was sputtered on a glass substrate
composed of alkali-free glass ("OA-10G", available from Nippon
Electric Glass Co., Ltd.) and then formed into a pattern by a
photolithography method. A photoresist SU-8 (available from Nippon
Kayaku Co., Ltd.) was applied, exposed, developed, and post-baked,
thereby forming an SU-8 pattern on the chromium pattern.
[0217] The resulting bank pattern was designed to be a pattern
including opening portions corresponding to 100 .mu.m.times.300
.mu.m subpixels and had a line width of 20 .mu.m and a thickness of
8 .mu.m. The BM substrate was used for the formation of a light
conversion layer.
[0218] A solid pattern was similarly formed. The contact angle of a
solvent (1,4-BDDA) used as an ink was measured and found to be
45.degree.. This indicated that the pattern was
solvent-repellent.
[0219] The red-light-emitting-nanocrystal-containing composition 3,
the green-light-emitting-nanocrystal-containing composition 3, and
the light-scattering composition ScB were ejected to the opening
portions with an inkjet printer (trade mane "DMP-2850", available
from FUJIFILM Dimatix). A head unit of the inkjet printer, the head
unit being configured to eject the inks, had 16 nozzles. The mount
of each of the ink composition used per ejection was 10 .mu.L per
nozzle.
[0220] A black matrix (hereinafter, also referred to as "BM") was
disposed on the platen (base table) of DMP-2850. The pattern of the
black matrix on the base and the scanning direction of the head
were matched. Alignment was performed. An ink was ejected to the
opening portions of BM at an ejection rate of 6 m/s.
[0221] The inks were ejected to form films in such a manner that
the thickness of the cured film of each ink was 80% or more of the
thickness of the bank of the black matrix. The thickness of the
cured film of the ink that had been applied by printing to the
opening portions of the BM and cured was measured with an optical
interference film thickness meter (Vert Scan).
[0222] The drying and curing treatment of the ink were performed as
described below.
[0223] In the case where the ink was a thermosetting ink, a solvent
was contained and thus evaporated under reduced pressure. In a
nitrogen atmosphere in a glove box, the ink was cured by heating at
100.degree. C. for 3 minutes and then 150.degree. C. for 30
minutes.
[0224] As described above, a pixel portion to convert blue light
into red light, a pixel portion to convert blue light into green
light, and a pixel portion that was composed of the
light-scattering material-containing dispersion free from a
light-emitting nanocrystal and that transmitted blue light (without
color conversion) were formed on the BM substrate. By the
above-described operation, a patterned light conversion layer 4
including the multiple pixel portions was formed.
(Production of Light-Emitting Device or Image Display
Apparatus)
(Production of Light-Emitting Device 1 and Image Display
Apparatuses 1A to 4A)
[0225] ITO electrodes were vapor-deposited on the light conversion
layers of the surfaces of the glass substrates including TFTs and
the light conversion layers 1 to 4. A light-emitting device 1
including an electroluminescent layer configured to emit blue light
was formed on each ITO electrode by a method described in "Appl.
Mater. Interfaces 2013, 5, 7341-7351". The ITO electrode and the
TFT layer were electrically connected through a contact hole.
Thereby, image display apparatuses 1 to 4 corresponding to the
light conversion layers 1 to 4 were produced. The light-emitting
device 1 including the electroluminescent layer configured to emit
blue light has a specific structure described below.
[0226] As the hole transport layer of the light-emitting device 1,
TAPC illustrated below was used.
##STR00011##
[0227] As the electron-blocking layer of the light-emitting device
1, mCP illustrated below was used.
##STR00012##
[0228] A compound illustrated below was used as a light-emitting
material (dopant) of the first light-emitting layer of the
light-emitting device 1.
##STR00013##
[0229] As the host material of the first light-emitting layer of
the light-emitting device 1, mCP illustrated below was used.
##STR00014##
[0230] A compound illustrated below was used as a light-emitting
material (dopant) of a second light-emitting layer of the
light-emitting device 1.
##STR00015##
[0231] As the host material of the second light-emitting layer of
the light-emitting device 1, UGH2 illustrated below was used.
##STR00016##
[0232] As the hole-blocking layer of the light-emitting device 1,
UGH2 illustrated above was used.
[0233] As the electron transport layer of the light-emitting device
1, a compound illustrated below was used.
##STR00017##
[0234] The hole transport layer, the electron-blocking layer, the
first light-emitting layer, the second light-emitting layer, the
hole-blocking layer, and the electron transport layer were formed,
in this order, by patterning on each ITO electrode. A
blue-light-emitting layer was formed by a method described in
"Appl. Mater. Interfaces 2013, 5, 7341-7351. A solid (LiF/Al)
electrode serving as a cathode and a solid protective layer were
formed and stacked in this order. Thereby, image display
apparatuses 1A to 4A including the light-emitting devices
configured to emit blue light were produced.
(Production of Light-Emitting Device 2 and Image Display
Apparatuses 1B to 4B)
[0235] ITO electrodes were vapor-deposited on the light conversion
layers of the surfaces of the glass substrates including TFTs and
the light conversion layers 1 to 4. A light-emitting device 2
including an electroluminescent layer configured to emit blue light
was formed on each ITO electrode by a method described in "J.
Mater. Chem. C, 2014, 2, 6040-6047". The ITO electrode and the TFT
layer were electrically connected through a contact hole. Thereby,
image display apparatuses 1B to 4B corresponding to the light
conversion layers 1 to 4 were produced.
[0236] The light-emitting device 2 including the electroluminescent
layer configured to emit blue light has a specific structure
described below.
[0237] As the hole transport layer of the light-emitting device 2,
TAPC illustrated below was used.
##STR00018##
[0238] As the electron-blocking layer of the light-emitting device
2, mCP illustrated below was used.
##STR00019##
[0239] A compound illustrated below was used as a light-emitting
material (dopant) of the light-emitting layer of the light-emitting
device 2.
##STR00020##
[0240] As the host material of the light-emitting layer of the
light-emitting device 2, mCPPO1 illustrated below was used.
##STR00021##
[0241] As the electron transport layer of the light-emitting device
2, a compound illustrated below was used.
##STR00022##
[0242] The hole transport layer, the electron-blocking layer, the
light-emitting layer, the hole-blocking layer, and the electron
transport layer were formed, in this order, by patterning on each
ITO electrode. A blue-light-emitting layer was then formed. A solid
(LiF/Al) electrode serving as a cathode and a solid protective
layer were formed and stacked in this order. Thereby, image display
apparatuses 1B to 4B including the light-emitting devices
configured to emit blue light were produced.
[0243] The color gamuts of the resulting image display apparatuses
1A to 4A and 1B to 4B were measured.
[0244] Comparisons of any of the image display apparatuses
including the light conversion layers with the conventional organic
EL apparatuses that did not include a light conversion layer
indicated that the former had expanded color gamuts.
REFERENCE SIGNS LIST
[0245] 1 substrate [0246] 2 first electrode [0247] 3 hole injection
layer [0248] 4 hole transport layer [0249] 5 light-emitting layer
[0250] 6 electron transport layer [0251] 7 electron injection layer
[0252] 8 second electrode [0253] 9 light conversion layer [0254] 10
overcoat layer (protective layer) [0255] 11 substrate [0256] 20
transistor layer [0257] 100 light-emitting device [0258] 101 image
display apparatus [0259] 701 capacitor [0260] 702 driver transistor
[0261] 703 power supply line [0262] 705 common electrode [0263] 706
signal line [0264] 707 scan line [0265] 708 switching
transistor
* * * * *